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<div class="rich-text">Virtual autopsies, 3-D fingerprints, and digital crime scenes are making crime-solving into a more precise science.
</div>

Forensics on Trial





  
      <div class="rich-text"><p>
	The twin threats of criminal misidentification and new technology that may allow criminals to act more anonymously than ever before are spurring researchers around the world to find new ways to better understand mysterious crimes and correctly identify their perpetrators.</p>
<p>
	"I would say, in my humble opinion, that any case could be solved given enough time, money and resources," says Arpad Vass, a chemical forensics researcher at Oak Ridge National Laboratory in Tennessee, referring to the promise of new forensic techniques.</p>
<h3>
	Sniffing Out Victims</h3>
<p>
	Often, the first step in identifying who committed a crime is identifying the victim. That's why Vass developed the Light-weight Analyzer for Buried Remains and Decomposition Odor Recognition system for locating dead bodies, known as LABRADOR for short.</p>
<p>
	"Finding clandestine graves has been a nemesis for over a decade now," he says.</p>
<p>

            <figure class="richtext-image full-width"><img alt="LABRADOR" class="richtext-image full-width" height="292" width="672"
            src="/wgbh/nova/media/images/three-advances-forensic-02.width-800.jpg"/><figcaption>LABRADOR was developed by scientists at the Oak Ridge National Laboratory to sniff for 30 classes of chemicals given off by decaying bodies.<div class="credit">Courtesy of Oak Ridge National Laboratory</div></figcaption>
            </figure>
            </p>
<p>
	The apparatus that is now being developed by the Agile Technologies company looks like a metal detector, but contains a small box on the end that collects air samples, Vass says. The box contains 12 sensors that respond to 30 classes of chemicals that decaying bodies emit. It also has both a visual display and an audio signal that relay information about chemical concentrations to the user. Criminal investigators can then scan areas and dig for bodies where those readings are highest.</p>
<p>
	Cadaver dogs are commonly used to find bodies, but dogs are unable to smell relative concentrations of chemicals as accurately as the LABRADOR. Ground water can move chemicals away from a decaying body by up to a kilometer, Vass says, so dogs often locate a person's scent far from the actual site of a body. But when the LABRADOR is used in conjunction with dogs, scientists can home in on the precise area where the chemicals are the most concentrated.</p>
<p>
	Additionally, the composition of the chemicals emitted give information about how long ago the person was killed, because as the body decomposes, the odor signature it emits changes.</p>
<p>
	In some cases, locating bodies provides crucial evidence to help link suspects to the crime. But other times the goal is simply to provide families with a sense of closure.</p>
<p>
	Vass says the LABRADOR was used in 2010 to find the body of Lynsie Ekelund, who had been reported missing in 2001. Detectives knew she had been buried somewhere on a 40-acre ranch, and the LABRADOR device enabled them to start digging within 15 meters of where her body was ultimately found.</p>
<h3>
	Detecting Chemical Impurities</h3>
<p>
	Across the country at the Pacific Northwest National Laboratory in Richland, Washington, chemist Carlos Fraga is working on a new forensic technique that also involves analyzing chemicals. But unlike Vass, he is trying to locate criminals, not victims.</p>
<p>
	Fraga's work focuses on a highly threatening form of terrorism: chemical attacks. He works for the Department of Homeland Security, which began a chemical forensics program in the aftermath of the 2001 anthrax attacks in the U.S.</p>
<p>
	Unlike bomb explosions or gunshots, which leave unique physical traces, detecting the origin of a chemical attack poses more of a problem for forensic scientists. A terrorist could easily release a potent gas in a large crowd and sneak away as its effects take hold, leaving behind nothing but a wave of sudden, and sometimes fatal, illness.</p>
<p>
	Fraga's team has figured out a way to trace the origin of a deadly chemical by analyzing its impurities. His lab has been working with sarin, a chemical agent that attacks the nervous system.</p>
<p>
	Each batch of sarin has a distinct amount of impurity that makes it unique from other batches. What separates Fraga's work from that of other scientists is that he is the first to show that the impurity pattern can reveal the type of chemicals from which the sarin was produced. That same impurity profile exists within the original chemicals as well, he says.</p>
<blockquote>
	Careful analysis is required to determine the probability that a piece of evidence and a suspect are linked.</blockquote>
<p>
	With Fraga's technique, chemicals at crime scenes could be matched to chemicals more closely linked to suspects. Police could also use it to map patterns of drug flow into their countries.</p>
<p>
	Fraga says the main problem right now is that no one is sure how reliable chemical tracing is. He says that TV shows like CSI often depict scenarios in which someone receives a piece of evidence and instantly exclaims, "It's a match!" But in reality, careful analysis is required to determine the probability that a piece of evidence and a suspect are linked. His team is working to discover what some of those probabilities are.</p>
<h3>
	Steps to Prevent Crime</h3>
<p>
	While Fraga's research centers around developing a method to find potential criminals, Marios Savvides is focusing on security systems that will help to prevent crime in the first place. For Savvides, each literal step forward is a metaphorical one as well; in his bio-pedometrics lab at Carnegie Mellon University, he is studying the unique imprint of a person's foot as he or she walks.</p>
<p>
	His work is part of a collaboration with Autonomous ID, the company that is funding the research at CMU and whose chairman and president Todd Gray developed the idea for the bio_sole, a device that measures the way in which a person's foot hits the ground to verify his identity. Such a device could replace measures that high-security areas now have in place to protect their privacy, such as fingerprint and retina scanning.</p>
<p>
	Gray says he was inspired to "resolve enemy impersonation" after an incident in January 2007 in which disguised insurgents infiltrated a U.S. army base and killed several soldiers.</p>
<p>
	The bio_sole will look like a Dr. Scholl's shoe insert but will measure the dynamics of a person's foot as they move—a characteristic unique to each individual. Savvides is currently developing algorithms to verify individuals' identities. His team is studying the differences in individuals' gaits and footprints, examining questions like how the device will be able to recognize a person's foot movements as they change with age, injury, or different forms of movement like running.</p>
<p>
	Fingerprint and retina scanning involve only a physiological means of verifying identity, which means that war enemies could cut off the required body part and use it to gain access to high-security areas. "There's different rules of engagement there," Gray says.</p>
<p>
	But the bio_sole uses both physiological traits—such as the way in which a person's foot is shaped—<em>and</em> behavioral traits—such as the way in which a person walks—to verify identity. Even if a potential insurgent cut off another person's foot, he would be unable to precisely mimic the way in which he walks.</p>
<p>

            <figure class="richtext-image full-width"><img alt="carousel-footprint" class="richtext-image full-width" height="394" width="672"
            src="/wgbh/nova/media/images/three-advances-forensic-01.width-800.jpg"/><figcaption>The way each person sets their foot down to create a footprint is unique, which scientists are exploiting to create new a new method of for identifying people.<div class="credit">Courtesy of LifeInMegapixels</div></figcaption>
            </figure>
            </p>
<p>
	Savvides says the bio_sole has other advantages as well. Facilities that rely on fingerprint or retina scans require people to pause and wait for a machine to authenticate them. If a person is wearing a hazmat suit or sterile gloves, the process can take even longer. In places like hospitals, where every second counts, such a delay could be life-threatening. The bio_sole, however, verifies someone's identity as they move naturally.</p>
<p>
	Additionally, with the bio_sole, all the information about an individual is contained within the shoe itself, eliminating some of the privacy issues and costs associated with other systems. With fingerprinting or retina scanning, databases of information used to verify people's identities must be secured and encrypted. But the bio_sole system is self-contained, meaning the sole itself simply sends a yes or no signal to an access point depending on whether it recognizes the individual wearing it, Gray says.</p>
<p>
	Savvides says the bio_sole could have other forensic applications as well. As his team researches individual foot dynamics, they may better be able to identify key traits of the person who left a footprint at a crime scene like his or her age, gender, and form of movement.</p>
<blockquote>
	Forensic tools that once seemed to belong in the realm of science-fiction are becoming more real every day.</blockquote>
<p>
	Though the bio_sole's applications are "potentially limitless," Savvides says his team still has to do more research to ensure that the sole can correctly identify a person across their entire range of foot movements. Additionally, they need to learn whether people's foot dynamics will change with age or illness to determine how often the device needs to be updated.</p>
<h3>
	Will Science Ever Stop Crime?</h3>
<p>
	New ways to detect odors, analyze chemical impurities, and identify individuals by their foot movements are just a few examples of the current scientific advances in crime-fighting techniques. Forensic tools that once seemed to belong in the realm of science-fiction are becoming more real every day. Scientists can now study a person's hair to determine what they have eaten and where they have been. They can use lasers to analyze the composition of liquids and gases without affecting the substance itself. In the future, it may even be possible to detect lies with brain scans, though such techniques have been met with intense skepticism thus far.</p>
<p>
	Despite the best efforts of scientists to advance forensic techniques—whether it's finding victims, catching criminals, or keeping areas secure—fighting crime is like shooting at a moving target, Gray says. "As the forensic sciences moves forward, so does the means of trying to circumvent those sorts of things."</p>
<p>
	Additionally, Vass says most law enforcement agencies are understaffed and lack the money to employ some of the technological advances.</p>
<p>
	While using new techniques is important, Fraga says, so too is understanding their limits. "It goes back into understanding the uncertainty and the limits of these techniques." he says. Forensic science "really has to be approached by the scientific method."</p>
<p>
	It is unclear whether advances in forensic technology will reduce the alarmingly high number of innocent people in prison. It seems unlikely that scientific developments alone will eliminate every possibility for error in the criminal justice system. But perhaps they will serve to cut the number of mistaken convicts in half—to say, the number of people found in Alaska's capital city, rather than Wyoming's.</p>
</div>
  



Sniffing, sifting, and sensing new ways to solve&mdash;and prevent&mdash;crime.

Three Advances in Forensics





  
      <div class="rich-text"><p>
	Seven years later, there were still no leads in the case. Desperate for a break, the state medical examiner released a sample of Saltair Sally's long, blonde hair to be tested by stable isotope analysis, a new forensic technique that had been introduced in the years since Saltair Sally had been discovered.</p>
<p>
	Every molecule in our bodies—including those found in hair—are made up not just of different elements, but of different ratios of stable isotopes of those elements. Take hydrogen, for example. In its most common form, it has one proton and one electron. There are also two less common isotopes, deuterium and tritium, which have one and two neutrons, respectively, in addition to their proton and electron. Deuterium is particularly useful to forensic scientists. It is naturally occurring and very stable, meaning it is found in water in varying amounts, and, critically, those variations depend on the source of the water.</p>
<p>

            <figure class="richtext-image full-width"><img alt="carousel-mass-spectrometer" class="richtext-image full-width" height="480" width="672"
            src="/wgbh/nova/media/images/stable-isotopes-01.width-800.jpg"/><figcaption>A time of flight secondary ion mass spectrometer (TOF-SIMS) used to analyze the stable isotope composition of surfaces.<div class="credit">Courtesy of Pacific Northwest National Laboratory</div></figcaption>
            </figure>
            </p>
<p>
	Lesley Chesson works at Salt Lake City-based IsoForensics, the company that received the hair sample. "It was our first case, where we really got started," says Chesson, an analytical chemist. "They contacted us to see if we would analyze the hair—a long length of the hair—looking at hydrogen and oxygen to see, Was she local? Did she move into the area? If she did, where was she from prior to her death?" Such clues would give investigators valuable information as they continued to search for the victim's identity.</p>
<p>
To see how that's possible, let's follow a raindrop from a cloud over the Pacific Ocean to Saltair Sally's strand of hair. When those clouds rain, the heavier, oxygen-18 containing water molecules will fall out first. That typically happens near the coast. As the rain cloud moves inland, it's constantly losing molecules with oxygen-18, and its raindrops become isotopically lighter and lighter. Since our drinking water comes from rainwater, people near the coasts drink water with more oxygen-18 atoms in it than people living inland. Those atoms eventually become a part of our tissues, like hair. 
<p>
	If Saltair Sally had been in Salt Lake City in the weeks preceding her death, the hair closest to her scalp would reflect the isotopic signature of Salt Lake City's local water supply. If she had been in, say, Seattle instead, her hair's isotopic composition would contain more oxygen-18, giving investigators a valuable clue.</p>
<p>
	"We analyzed the hair sample," Chesson says. "It looked like within the two years leading up to her death, she had been a frequent migrant. She had moved at least three or four times, and it seemed she was making this sort of cyclic pattern. She was in a region consistent with Salt Lake City and the Intermountain West, and then she was moving someplace more towards the northwest. She did this a couple of times in the years leading up to her death."</p>
<p>
	Armed with this new information, detectives refocused their investigation on the regions Chesson and her colleagues had suggested. Still, it wouldn't be until August 2012 that they received a break in the case.</p>
<h3>
	More than water</h3>
<p>
	Hair isn't the only tissue scientists can analyze for clues. Fingernails are nearly identical in composition to hair, and like hair, they leave an isotopic timeline that remains unchanged until it gets cut off. In fact, every part of our bodies has potentially exploitable isotopic signatures. Though hydrogen and oxygen in hair and fingernails are often the first to be analyzed, other isotopes and body tissues can provide different types of information, says Wolfram Meier-Augenstein, a professor and principal scientist at the James Hutton Institute in Aberdeen, Scotland.</p>
<p>
	"Very rarely is one isotope alone the thing that will solve the case," he says. "It is usually a combination. Forensic science is all about context. We usually aim to build a picture not relying on one technique."</p>
<p>
	Carbon and nitrogen are two other elements commonly used by forensic scientists. Like hydrogen and oxygen, carbon and nitrogen are found throughout our bodies. But instead of chronicling the water supply, they reflect people's diets. Carbon in our bodies is largely derived from plant tissues, which get their carbon from CO<sub>2</sub> in the atmosphere. Carbon isotopes are concentrated differently depending on which type of photosynthesis a plant uses. Wheat, rice, and sugar beets use what's known as C3 photosynthesis. Their cells take CO<sub>2</sub> directly from the atmosphere to convert to sugar. Corn, sorghum, and sugar cane use a different photosynthetic pathway known as C4, which has an additional enzyme that concentrates CO<sub>2</sub> before handing it off to Rubisco, which begins the carbon fixing process. The added step in C4 plants increases their carbon-13 levels relative to C3 plants. In North America, where corn is common in diets, people's tissues tend to have high carbon-13 concentrations.</p>
<blockquote>
	"We don't find a needle in a haystack. We reduce the haystack to a manageable size."</blockquote>
<p>
	Nitrogen isotope levels depend on whether people are omnivorous, vegetarian, vegan, or otherwise. Each step up the food chain enriches the ratio of nitrogen-15 to nitrogen-14 by 3.4‰ (per mille). That means the tissues of a person who is vegan will have less nitrogen-15 than the tissues of someone who eats mostly meat. Such clues about a victim's diet can be helpful when police are canvassing for clues.</p>
<p>

            <figure class="richtext-image full-width"><img alt="tooth" class="richtext-image full-width" height="480" width="672"
            src="/wgbh/nova/media/images/stable-isotopes-02.width-800.jpg"/><figcaption>Stable isotopes in teeth provide investigators with detailed records of where a person was living when they were formed. Unlike other tissues in the body, the isotopic composition of teeth never change.<div class="credit">Courtesy of Wolfram Meier-Augenstein</div></figcaption>
            </figure>
            </p>
<p>
	Unlike hair and fingernails, most tissues do not record in linear fashion where a person was or what they ate. "While the signature in hair will change relatively rapidly, the signature in other tissues, bone for instance, will change very, very slowly. The signature in teeth won't change at all," Meier-Augenstein says. Turnover in muscle tissue, which you might think would happen quickly, is a slow process. "Depending on which muscle we would probe, it would take three to six months before everything in the soft tissue department would have changed."</p>
<h3>
	Chemically identical, isotopically distinct</h3>
<p>
	Analyzing human tissue in cases like Saltair Sally's is an obvious application of stable isotopes, but it isn't the only one. Meier-Augenstein frequently deals with drug-related cases, including one in the United Kingdom where a man was initially arrested on the street for possessing five tablets of MDMA, or ecstasy. It's a minor offense, but the police felt he might have been hiding something.</p>
<p>
	"The police secured a search warrant and searched his place, and lo and behold, in a gym bag in a wardrobe, they found a huge plastic bag with thousands of ecstasy tablets," Meier-Augenstein recounts. The suspect denied knowledge of the stash, instead blaming it on a friend. Though the tablets looked and were chemically to similar to the five found on the suspect, police didn't feel it was enough for a solid conviction, Meier-Augenstein says. That's where stable isotopes came in. "These tablets were analyzed isotopically, and lo and behold, at a 95-plus percent confidence level, there was absolutely nothing to choose between them." Confronted with this new evidence, the suspect admitted his guilt.</p>
<p>
	Drug-related cases aren't the only type where stable isotope forensics can augment traditional chemical analysis. Today, many products are chemically identical, even if they are from separate factories. Take, for example, white paint chips found on a crime scene, Chesson says, or traces of explosives used in a terrorist attack. Evidence from the crime scene may chemically match those found in a suspect's home, but stable isotope analysis could reveal that they were made in separate factories. If that were a key piece of evidence, the isotopic analysis could be enough to keep an innocent person out of prison.</p>
<p>
	Stable isotopes can also distinguish genuine products from counterfeits. The liquor industry, which is rife with fakes and mislabeled products, has found isotopic analysis to be particularly useful. Wine may be intentionally mislabeled as a better vintage, or a cheap single-malt whiskey could be hawked as an upscale brand. By comparing a suspected counterfeit with an original sample, stable isotopes can help investigators unmask the fraud.</p>
<h3>
	isotopic filters</h3>
<p>
	Though stable isotopes are useful in sniffing out potential counterfeits—or potential leads in a case—they are not a means of identification, like fingerprints or DNA. "I really don't like the word identification, because that's not what we do," Meier-Augenstein says. "We try to create a picture of the person's life and life circumstance that hopefully helps jog a person's memory."</p>
<p>

            <figure class="richtext-image full-width"><img alt="Autosampler" class="richtext-image full-width" height="480" width="672"
            src="/wgbh/nova/media/images/stable-isotopes-03.width-800.jpg"/><figcaption>Samples being loaded into a mass spectrometer for analysis.<div class="credit">Courtesy of Lesley Chesson</div></figcaption>
            </figure>
            </p>
<p>
	Meier-Augenstein recommends viewing each stable isotope as a filter. In our globalized world, a John Doe could have come from anywhere. Investigators start looking for clues close to where the victim was found, but if nothing turns up, they could end up combing through every missing persons list in the world.</p>
<p>
	Stable isotopes help narrow that search. Deuterium and oxygen-18 from a victim's hair or fingernails "can exclude 80 or 90 percent of the world," Meier-Augenstein notes. A nitrogen-15 analysis of the victim's muscle tissue could reveal that he was a vegetarian, another useful clue. And heavier isotopes such as strontium leech from rocks into groundwater, eventually making their way into our bones and teeth.</p>
<p>
	Together, all of these clues narrow the field of potential matches, greatly simplifying things for detectives. "We don't find a needle in a haystack," Meier-Augenstein says. "What we do, in an ideal circumstance, is we reduce the haystack to a manageable size."</p>
<h3>
	what the future holds</h3>
<p>
	While stable isotopes have proven themselves useful, they aren't staples of forensic science—yet. Part of the problem is cost. Stable isotope analysis isn't cheap. Preparing samples takes lots of time and involves a host of costly chemicals. Most samples today are run through mass spectrometers, which are large, expensive, and often temperamental. Finally, interpreting the data requires an expert. These obstacles aren't insurmountable, but they're not insignificant.</p>
<p>
</p>
<p>
	To change that, Meier-Augenstein thinks a landmark case needs to hinge on evidence provided by stable isotopes. "There will be a major case, unfortunately it will involve something very unpleasant," he says. "My money would probably be on terrorism, as sad as the prospect might be, or it's a high profile murder case where isotopes provide the clincher."</p>
<p>
	Chesson is more optimistic. She feels that breakthroughs in equipment used to process stable isotopes samples will spur widespread adoption. Currently she is testing a new device that uses a laser to measure isotopic ratios. It doesn't require samples to be as carefully prepared, and it doesn't take up nearly as much space as a typical mass spectrometer. Chesson foresees a day when that technology could be further miniaturized to where it can fit on countertops or even in the trunks of detectives' cruisers.</p>
<p>
	"You could take your analyzer places that you couldn't before, which means you can analyze things that are harder to collect and get back to lab. That decreases costs, speeds up time, and opens up a whole new set of samples that you could possibly analyze," she says. "Anything that decreases cost and increases throughput will always help this type of analysis. That's why DNA analysis really exploded."</p>
<h3>
	Naming saltair sally</h3>
<p>
	Salt Lake Unified Police announced on August 7, 2012 that, with the help of stable isotope analysis, they had identified Saltair Sally. Her name was Nikole Bakoles. The cyclic pattern of travel between Salt Lake City and Seattle recorded in Saltair Sally's hair matched information provided in Bakoles's missing persons report, which had been filed in 2003. A DNA test confirmed the match. Bakoles, who was 20 at the time of her death, was last seen in March 2000, when she was living in a hotel in a southern suburb of Salt Lake City with her boyfriend and young child. In the preceding years, she had traveled to Seattle occasionally to visit family members, a habit which was clearly recorded in the isotopic composition of her hair. Without that information, it's likely Saltair Sally would still be a cold case.</p>
<p>
	Given where Bakoles's remains were found and the manner in which they were disposed, police suspect foul play. Stable isotopes haven't led to an arrest yet, Chesson says, "but we did help finally put a name to a person, which was really pretty cool."</p>
</p></div>
  



Investigators use elemental variations to unearth new leads.

Stable Isotopes in Forensics

<p></p>
<p>Can a team of forensic archaeologist identify three WWII airmen that disappeared?</p>
<p>In 1944, three WWII airmen disappeared beneath the waves. Now, there may be hope for the return of their remains. The Department of Defense, which operates the largest forensic anthropology lab in the world, does a skeletal analysis to figure out if the recovered remains belong to more than one individual. Then the Armed Forces Medical Examiner System takes over to conduct a DNA analysis using family samples.</p>
<p><b>Identifying Lost Crew with Forensics and DNA Analysis</b></p><p>Published: December 3, 2018</p><p></p><p><b>Onscreen</b>: Dec 17, 1944: A B-24 bomber was shot down off Croatia. Three airmen disappeared beneath the waves: Pilot Eugene Ford, Navigator Russel C. Landry, and Flight Engineer Charles E. Priest.</p><p>Now, there may be hope for the return of their remains. The Department of Defense operates the largest forensic anthropology lab in the world.</p><p><b>Tyler Dunn</b>: It’s my job to do a skeletal analysis blind, so I don’t bias myself.</p><p>We were presented with 11 teeth; a right humerus, that’s relatively intact compared to everything else; a fragment of a vertebra; a handful of, sort of, non-diagnostic long bone fragments—we can more or less just tell that they’re bone; some fingers, a bit of a toe, and then most of the lower right leg, so a tibia and a fibula.</p><p>The first question I generally ask is the minimum number of individuals. So, we try and figure out if this could be, or is, more than one person.</p><p>Based on this case, the skeletal—it’s called M.N.I. or &quot;minimum number of individuals&quot; — the skeletal M.N.I. is one. I have good reason to think that this is one individual.</p><p><b>Onscreen</b>: This conclusion is backed up by the dental analysis.</p><p><b>Dunn</b>: So, I can tell that this is all teeth from one individual, based on tooth shape, the size of the tooth, and more or less what they look like.</p><p><b>Onscreen</b>: It appears that only a single airman was recovered, based on the skeletal evidence. But who was it?</p><p><b>Dunn</b>: We more or less measure how long the tibia is. The stature for this individual that we estimated was right around 5 foot 10.</p><p><b>Onscreen</b>: Yet the skeletal remains alone cannot provide a definitive ID, so they turn to DNA. The Armed Forces Medical Examiner System now takes over.</p><p><b>Timothy McMahon</b>: This is where we take the unknown and we put a name to them.</p><p><b>Onscreen</b>: First they extract DNA from the bones and teeth and then sequence many different regions. Then they compare the sequence against family reference samples until finally a match is confirmed.</p><p>Seven months later…</p><p><b>Jim Bell</b>: …so, based on that, the laboratory analysis, established remains of those as First Lieutenant Eugene Ford, serial number Oscar 805804, U.S. Army Air Forces.</p>
<p></p>
<p></p>
<p></p>

<p>Can a team of forensic archaeologist identify three WWII airmen that disappeared?</p>

Identifying Lost Crew with Forensics and DNA Analysis





  
      <div class="rich-text"><p>David Camm lost 13 years of his life to eight drops of blood.</p><p>In 2000, the Indiana state trooper was <a href="https://www.law.umich.edu/special/exoneration/Pages/casedetail.aspx?caseid=4291">charged with murder</a> after finding his wife and two children shot to death in their home. During the three trials that followed, the prosecution brought in bloodstain experts who argued that the flecks of blood on the t-shirt Camm had worn the night of the murder were “high-velocity impact spatter”—proof, they said, that he was the shooter. Analysts called by the defense, on the other hand, testified that the blood was actually a transfer stain that had smeared onto Camm’s clothing after he’d tried to help his children.</p><p>Testifying for the defense, forensic scientist Robert Shaler disputed the claims of the bloodstain experts on both sides, insisting that the blood’s scant patterning was “too little information from which to draw any meaningful conclusion,” Pamela Coloff at <i>ProPublica</i> <a href="https://www.propublica.org/article/bloodstain-pattern-analysis-jury-wrongful-conviction-acquitted-exonerated">reported last year</a>.</p><p>Nevertheless, spatter evidence was used against Camm, who was sentenced to 195 years in prison. He remained behind bars until his acquittal in 2013, after the conviction of another man whose DNA had been found at the crime scene several years before.</p></div>
  

  
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      <div class="rich-text"><p>Camm’s case is only one of many that have come under fire for their heavy reliance on bloodstain pattern analysis, a subfield of forensic science criticized in <a href="https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf">a report released by the National Academy of Sciences</a> in 2009 for being “more subjective than scientific” and rife with “enormous” uncertainties.</p><p>But that might be in the process of changing—thanks in part, perhaps, to the work of a team of physicists that’s marrying the study of blood spatter to fluid dynamics. Their <a href="https://aip.scitation.org/doi/10.1063/1.5111835">latest model</a>, published today in the journal <i>Physics of Fluids,</i> can now accurately match a bullet of a certain size and shape to the size, number, and speed of blood droplets produced by a gunshot wound.</p><p>The approach is all about bringing bloodstain pattern analysis up to speed with modern science, says <a href="https://www.exponent.com/professionals/c/comiskey-patrick">Patrick Comiskey</a>, who conducted the research as part of his graduate work at the University of Illinois, Chicago. Unlike an individual investigator’s interpretation, he says, physics is something “you can’t change.”</p><p>No one scientific finding or model will solve all the problems associated with bloodstain pattern analysis, says <a href="https://forensics.wvu.edu/faculty-and-staff/faculty/suzanne-bell">Suzanne Bell</a>, a forensics expert at West Virginia University who was not involved in the research. Still, she says, “any time you bring in fundamental science to forensic applications…[it] will help build up the base knowledge we didn’t have necessarily before. People have been working with bloodstains for hundreds of years, but we haven’t seen the depth of investigation that studies like this bring.”</p><p><b>Shaky foundations</b></p><p>Bridging the existing gaps between forensics and science isn’t trivial. There’s an inherent challenge to analyzing crime scenes, which are, in a sense, the world’s worst time capsules: At best, they partially preserve the remains of a complex, messy problem that can only be solved in reverse.</p><p>In many cases, the pattern left by a bloodstain, including the number, size, location, and overall distribution of droplets, can reveal a lot about the shooter, victim, and weapon involved. But some of the methods that blood spatter analysts have used in the past to reverse engineer the trajectory and point of origin of a stain <a href="https://www.sciencedirect.com/science/article/pii/S0379073813002417">may have been too simple</a>, leaving out some of the intricacies of how blood moves and deforms after leaving the body, says <a href="https://www.me.iastate.edu/directory/faculty__trashed/daniel-attinger/">Daniel Attinger</a>, a mechanical engineer at Iowa State University.</p>
            <figure class="richtext-image full-width"><img alt="shutterstock_1039696972.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/iStock-961710198_lSqcTWD.width-800.jpg"/><figcaption><p>Many factors, including the speed of a bullet, the distance blood spatter travels, and the type of surface it lands on, affect the number, size, location, and distribution of the droplets that make up a bloodstain. Image Credit: undefined undefined, iStock</p><div class="credit"><p></p></div></figcaption>
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            <p>Part of the problem is that blood isn’t an easy fluid to work with. Liquids like water flow at the same rate no matter how hard they’re shaken or stirred, but the same isn’t true of certain mixtures like ketchup or blood, which actually get <i>runnier</i> if more force is applied to them. As a result, blood drips slow, but sprays fast.</p><p>Blood is also incredibly dynamic: It teems with living cells and active enzymes, and its properties shift under the influence of minute fluctuations in temperature, or the presence of drugs. It’s the “most complex fluid” he’s ever studied, Attinger says.</p><p>As soon as it leaves a human body, blood begins to cool and coagulate, effectively thickening, while also warping under the combined influence of gravity and drag from the air it’s moving through.</p><p>That’s all before blood meets <a href="https://www.sciencedirect.com/science/article/pii/S0379073818310600?via%3Dihub">the surface it ultimately lands on</a>—the properties of which can seriously affect the impressions left behind. If blood’s landing pad has some bounce, it will affect the way the fluid splashes; if it’s rough or full of holes, it’ll change how the blood distributes itself. And while some stains burst on impact, producing a spray of disconnected droplets, others sprout spines that snake away from the bloody epicenter like skeletal fingers.</p><p>Like several other disciplines of forensics based in pattern analysis, the study of blood spatter arose and <a href="https://www.pnas.org/content/115/18/4541">matured largely outside of the scientific community</a>, Bell says. Unlike DNA analysis, which was honed in research laboratories for the purposes of basic biology before being applied to forensics, blood spatter has a far more subjective heritage, based on experiences, anecdotes, and empirical observations. “To get their data, analysts would walk into a room, fill a sponge with blood, and hit it,” she says.</p><p>There was nothing intrinsically wrong with this practice, and this kind of experimentation remains necessary, she says. But the practice lacked strong scientific foundations, and for years, little was done to explore the fundamental dynamics behind the paths droplets of blood took after impact.</p><p><b>Thicker than water, and far more complex</b></p><p>This rift in knowledge is where fluid dynamics comes in: Many of the subtleties of blood in motion can be captured with equations, Comiskey says. He, Attinger, and their colleagues have spent years crunching the numbers, coming up with increasingly complex theoretical models that account for more and more of the blood spattering process. The team did their fair share of hands-on experiments, too, firing bullets at everything from <a href="https://pdfs.semanticscholar.org/9fea/843e16fd242d07d5db8b13606f4a3649dd0d.pdf">sponges soaked in pig’s blood</a> to suspended sacks filled with the <a href="https://aip.scitation.org/doi/10.1063/1.5111835">real stuff taken from human bodies</a>. After collecting the spatter on clean, smooth surfaces like butcher paper, they’d see how the results of their computer simulations stacked up, and adjust accordingly.</p>
            <figure class="richtext-image full-width"><img alt="spatter setup.jpg" class="richtext-image full-width" height="494" width="800"
            src="/wgbh/nova/media/images/shooting_setup_3.1.width-800.jpg"/><figcaption><p>The Attinger lab&#x27;s experimental setup for collecting blood spatter. Image Credit: Courtesy of Daniel Attinger, Iowa State University</p><div class="credit"><p></p></div></figcaption>
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            <p>The researchers’ models can now demonstrate a mathematical relationship between the <a href="http://aip.scitation.org/doi/full/10.1063/1.5111835.">shape</a> and speed of a bullet and the distribution of the resulting blood spatter. Some things are fairly intuitive—like the fact that faster bullets will generate smaller droplets, or that the farther a fleck of blood travels, the more it’s going to be influenced by the pull of gravity. Other factors, though, are more subtle, such as the ways in which droplets are affected by the gas that escapes the muzzle of a gun after it’s fired.</p><p>“We now have a <a href="http://aip.scitation.org/doi/full/10.1063/1.5111835.">pretty generalized model</a>,” Comiskey says. “I can say, more or less, that if I have this number of droplets, and they’re this size, and so on, then it was this bullet, this velocity, and [the shooter or victim was at] this location.”</p></div>
  

  
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      <div class="rich-text"><p>One of the most important factors, Comiskey says, is being able to predict how blood breaks up into smaller drops, a process called atomization. Blood spatter progresses in two directions—<a href="https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.2.073906">backward, toward the shooter</a>, and <a href="https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.3.063901">forward, parallel to the path of the bullet</a>—and neither is very straightforward. The backward case is actually the simpler one, because it doesn’t really matter what the bullet is hitting: Either way, it’ll produce a kind of recoil. Forward spatter, however, produces more droplets that can <a href="https://www.sciencedirect.com/science/article/pii/S0379073817301536?via%3Dihub">travel up to twice as fast</a>. It also involves messier physics, because the blood is pushed so quickly ahead of the bullet that it shatters like glass instead of deforming like a typical fluid. The term for this phenomenon is an apt one: “chaotic disintegration.”</p><p>Comiskey compares the two physical processes to running a faucet into a cup already filled with liquid. Backward spatter is the upward splash that occurs when the water hits what’s in the cup. Forward spatter is what’s produced when the jet of water is so fast and strong that it blasts through the bottom of the cup. In this case, the cup’s composition and contents can have huge effects on the resulting spray.</p><p>Attinger acknowledges that these models and scenarios are still oversimplifications. Sponges and sacks of blood aren’t human bodies, and the walls and floors of crime scenes usually aren’t lined with paper. The different types of fabric used in clothing also present a complication that hasn’t yet been accounted for in crime scene reconstruction. Still, experiments like these, in which the researchers can control and keep track of all the main variables at play, are necessary starting points, he says.</p><p>“None of this fundamentally changes what happens if you hit a sponge full of blood,” Bell says. “But it helps you understand why it produces the pattern it produces.”</p><p><b>Blood will tell—but just how much?</b></p><p>The researchers hope that their models will someday become sophisticated and realistic enough to be translated into a chart that spatter analysts can use in the field. An even loftier goal, Comiskey says, would be a cell phone app or handheld device that could scan photos of stains and spatter, crunch the numbers, and spit out a likely rundown of what transpired: the type of gun, the bullets used, the locations of the people involved, each with a score of the algorithm’s confidence in its results.</p><p>That possibility is a long way off, though, says <a href="https://forensicscience.vcu.edu/people/miller-edd.html">Marilyn Miller</a>, a forensics expert at Virginia Commonwealth University who was not involved in the research. Perfect experimental conditions manufactured in a research lab are a far cry from the “highly textured, highly interrupted world of a crime scene,” she says.</p><p>All the same, the team’s results offer clarity and coherence to the study of blood spatter, Miller says. “This is the kind of fundamental research that should be the basis for all forensic sciences.”</p>
            <figure class="richtext-image full-width"><img alt="backspatter fabric strips.jpg" class="richtext-image full-width" height="434" width="800"
            src="/wgbh/nova/media/images/backspatter_fabric_strips_zTtNv0S.width-800.jpg"/><figcaption><p>In their simulations, researchers at Iowa State University collect blood spatter (in this case, backward spatter) on two different types of fabric. Image Credit: Courtesy of Daniel Attinger, Iowa State University.</p><div class="credit"><p></p></div></figcaption>
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            <p>Attinger, Comiskey, and their colleagues also aren’t alone in their work: Several other research groups have previously investigated the fluid dynamics of blood spatter, including teams at <a href="https://www.ncjrs.gov/pdffiles1/nij/grants/251439.pdf">Georgia Tech</a>, <a href="https://www.sciencedirect.com/science/article/pii/S0379073818310600">Boston University</a>, and <a href="https://aapt.scitation.org/doi/abs/10.1119/1.3591319?journalCode=ajp">Washington State University</a>.</p><p>Practically speaking, the mathematical models that come out of these labs could be incredibly powerful tools to test hypotheses generated in the field, Bell says. “The evidence might suggest that a blow was struck <i>here</i>, using <i>this,</i>” she says. “The model can tell you if that’s within the realm of possibility, or unlikely. It’s not going to be, ‘This is what happened,’ but it can assign a probability [to a scenario].”</p><p>And that kind of uncertainty—or lack thereof—can make a big difference as evidence makes its way into a courtroom, Bell says. “This is all about making something that wasn’t quantitative, more quantitative.”</p><p>But this knowledge won’t do any good if it’s not made available to blood spatter analysts in an understandable, approachable way, Miller says. The fact remains that most experts in this discipline haven’t been trained to interpret research papers grounded in fluid dynamics.</p><p>Bell agrees, stressing that much of the scientific gap in these disciplines is about communication, rather than a lack of effort or any kind of willful ignorance. “The problem isn’t that labs don’t want to do better,” she says. “It’s a resource issue: So much is demanded of [the personnel in forensics laboratories], who are busy doing cases...every minute they give to training, learning, and digesting this research takes away from casework.”</p><p>Tweaking training regimens for blood spatter analysts or encouraging academic researchers to join forensics labs might make a dent in these issues, Bell says. But more sweeping reforms will be needed to actually put research like this in a position where it can have a real impact.</p>
            <figure class="richtext-image full-width"><img alt="timeseries spatter.jpg" class="richtext-image full-width" height="398" width="800"
            src="/wgbh/nova/media/images/full_time_series.width-800.jpg"/><figcaption><p>Selected frames of video that recorded a simulation of a shooting. A 9 millimeter bullet was shot at a target about 35 inches away. Image Credit: Courtesy of James Michael and Reetam Das, Iowa State University</p><div class="credit"><p></p></div></figcaption>
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            <p>Part of this will require bringing other relevant voices, like those of judges and attorneys, into the bigger conversation, says <a href="https://www.innocenceproject.org/teams/#SarahChu">Sarah Chu</a>, the Innocence Project’s Senior Advisor on Forensic Science Policy, who was not involved in the research. Accuracy and scientific rigor are critical, but research also needs to be evaluated for its impact on the criminal justice system itself, as well as its ability to be ethically applied in the field, she says.</p><p>But the forecast isn’t necessarily gloomy, Chu says. In the decade since the 2009 National Academy of Sciences report, a lot has changed. In 2013, the National Institute for Standards and Technology and the Department of Justice established the <a href="https://www.nist.gov/topics/organization-scientific-area-committees-forensic-science">Organization of Scientific Area Committees (OSAC) for Forensic Science</a>, which was explicitly tasked with shoring up the scientific foundations of forensics.</p><p>OSAC’s subcommittees, which vet methodology for 25 forensic science disciplines, including <a href="https://www.nist.gov/topics/forensic-science/bloodstain-pattern-analysis-subcommittee">bloodstain pattern analysis</a>, are some of the few venues in which judges, attorneys, scientists, and other stakeholders are able to come together, Chu says.</p><p>Maintaining the momentum gained in the past 10 years, she says, will mean staying engaged and highlighting the goals that traditionally disparate communities have in common, rather than the qualities that might set them apart.</p><p>“There hasn’t been a lot of overlap between the world of these scientists and [bloodstain pattern analysts],” she says. “Hopefully publications like these signal the need for that to change.”</p></div>
  

  
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<p>Researchers are using fluid dynamics to try to improve the study of crime scene blood spatter.</p>

There will be blood, and physics, too: The messy science of bloodstain pattern analysis





  
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<span class="qa-start">Q:</span> Is your photo on this page a composite? The white-spot locations are different for both eyes—your left eye has more spots. Also, each half of your face, when viewed separately, has its own personality—the left side is perky and cocky-looking, while the right side seems tired and the smile looks forced. <span class="attrib">Stephen Donovan, Norristown, Pennsylvania</span></p>
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<span class="qa-start">Hany Farid: </span> Stephen, you have a good eye. The photo is not a composite, but it has been altered to enhance the contrast and color. You are right that my right eye shows only the reflection of one light, while my left eye shows the reflection of two lights. This is because the angle between my right eye and the second light is such that the reflection landed outside of my iris. The human face does generally have asymmetries, which is what you are noticing (and apparently some days my personality has asymmetries as well).</p>
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<span class="qa-start">Q:</span> Is it possible to fake an image so well that it can trick digital-forensics software? There must be people who are working as hard to defeat forensics detectives as you are trying to tease out the forgeries. <span class="attrib">Scott, Yakima, Washington</span></p>
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<span class="qa-start">Farid: </span> Scott, although not easy, it is definitely possible to create a fake good enough to fool all modern digital forensic techniques. I have created such fakes. As with the spam/anti-spam and virus/anti-virus game, the forensics/Photoshop game will continue to evolve with both sides becoming more and more sophisticated as the years go on.</p>
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<span class="qa-start">Q:</span> How do you think issues of digital fakery will impact the judicial and legislative process in the future? What advice do you have for those of us working in the law-enforcement sector? <span class="attrib">Lee Lerussi, Ohio</span></p>
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<span class="qa-start">Farid: </span> Lee, the impact of digital fakery is already affecting the judicial and legislative process. For example, the U.S. Supreme Court recently ruled that virtual (computer-generated) child pornography is protected under the First Amendment. In so doing, the Court's decision has made it difficult to prosecute violations of the child pornography laws, since it is easy to claim that images are not real, and difficult to prove that they are. Similarly, it is easy for anyone to simply claim that an audio recording, image, signed document, or video has been altered, leaving the court to contend with complex questions of authenticity.</p>
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			As technology continues to advance, and as digital imaging becomes more ubiquitous, these issues will only become more widespread and more complicated. As a result, it is important that the law-enforcement sector keep up with the fast pace of technology. And it is equally important that the field of digital forensics evolve to help the courts and other sectors contend with these issues.</p>
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<span class="qa-start">Q:</span> I work for a police-department photo lab, where we are very interested in obtaining your software. When will it be available? Can anyone get a copy? <span class="attrib">Joe Riplinger, Norfolk, Virginia</span></p>
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<span class="qa-start">Farid: </span> Joe, we are in the early stages of commercializing our image forensic software and hope to have a version ready for law-enforcement agencies some time next year.</p>
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<span class="qa-start">Q:</span> Could your software be used to uncover hidden things in videos, such as the movement of lips behind a beard? <span class="attrib">Al Hopfer, Arlington Heights, Illinois</span></p>
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<span class="qa-start">Farid: </span> Al, our work does not directly address this type of question, but there are techniques in image and video enhancement that might be applicable.</p>
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<span class="qa-start">Q:</span> Can your software provide any information on more subtle tweaks done on real photos, such as brightening, light airbrushing, or age progression? <span class="attrib">Ethan B., Canton, Ohio</span></p>
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<span class="qa-start">Farid: </span> Ethan, given the original resolution image, some of our techniques can determine if an image has been manipulated in any way from the time of recording. With a reduced resolution or heavily compressed image, other techniques are not as effective at determining more subtle alterations such as brightening or color adjustments.</p>
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<span class="qa-start">Q:</span> What is the minimum resolution or the smallest image size that your system can work with? <span class="attrib">Nate F., Rochester, New York</span></p>
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<span class="qa-start">Farid: </span> Nate, in general, the higher the resolution of the image, the easier it is to apply many image forensic tools. While there is no absolute lower limit, images smaller than 200 x 200 pixels begin to pose significant challenges for most forensic techniques.</p>
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<span class="qa-start">Q:</span> Have you looked at depth of field to identify fakes? What is the likelihood that two different photos, presumably taken with two different cameras, will have precisely the same depth of field? <span class="attrib">Deborah Haddow, Wells Bridge, New York</span></p>
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<span class="qa-start">Farid: </span> Deborah, this is an interesting question. The aperture size is the primary determinant of depth of focus. (A large aperture yields a narrow depth of focus, while a small aperture yields a large depth of focus.) It is quite possible that photos taken with different cameras yield the same depth of focus—particularly with point-and-shoot cameras, where the range of aperture sizes is limited.</p>
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			The depth of focus can, however, be a useful visual clue to determine the conditions under which an image was taken. For example, a large depth of field, where nearby and distant objects are equally in focus, implies that the image was photographed with a small aperture. A small aperture implies a small amount of light entering the camera, which means that a relatively long exposure time was needed to provide enough light to properly expose the image. A long exposure time often leads to motion blur (objects that are in motion being blurred in the image). Inconsistencies in these visual clues should raise questions of authenticity.</p>
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<span class="qa-start">Q:</span> How can someone with a limited knowledge of photo-editing software determine if a photograph is fake or real? Are there any "tricks" the average Joe should know? <span class="attrib">Joe M., Huntsville, Alabama</span></p>
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<span class="qa-start">Farid: </span> Joe, there are some visual clues that can be useful in looking for fakes. (Go to the <a href="http://www.pbs.org/wgbh/nova/sciencenow/0301/03-fakeorreal.html">Fake or Real?</a> audio feature for some hints.) Differences in lighting, differences in focus, differences in image quality, can each be useful in spotting a fake (see also Deborah Haddow's question above). However, care must be taken, as sometimes legitimate photos may, at first glance, appear to be fakes (see, for example, the response to the first question).</p>
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<span class="qa-start">Q:</span> In your opinion, what is the best photo manipulation software? <span class="attrib">J. Kelso, Eatonville, Washington</span></p>
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<span class="qa-start">Farid: </span> Adobe Photoshop is one of the most sophisticated and most popular photo editing software packages. We routinely use Photoshop in my lab to manipulate photos that we then use to test our forensic analysis tools.</p>
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<span class="qa-start">Q:</span> There has been a lot of controversy over the decades on the "backyard photographs" of Lee Harvey Oswald holding a rifle and some Communist Party newspapers. Do you know if these images are authentic? If you haven't looked at them yet, do you plan to? <span class="attrib">Jim Hain, Buffalo, New York</span></p>
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<span class="qa-start">Farid: </span> Jim, I have looked at these photos. While there are some peculiar lighting artifacts, they do not necessarily point to photo manipulation. The quality of the photos I have seen is too poor to permit a complete analysis.</p>
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<span class="qa-start">Q:</span> Did Robert Peary really reach the North Pole? There is a famous photograph that purports to show Peary and his companions very near 90 degrees north. But some scholars have called into question whether the direction of the lighting is consistent, astronomically. You simply must bring your expertise to bear on this fascinating historical controversy! <span class="attrib">George Desnoyer</span></p>
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<span class="qa-start">Farid: </span> George, I have not looked at these photos. We have, however, analyzed the original moon landing images and found that the lighting in all of the photos is consistent, including consistent with the expected position of the sun given the landing location and the date.</p>
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<span class="qa-start">Q:</span> Do the Associated Press or major newspapers like the Los Angeles Times ever check to see if the photos they publish or send through the wire have been manipulated? <span class="attrib">Don Kroster, Los Angeles, California </span></p>
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<span class="qa-start">Farid: </span> Don, the Associated Press processes over 10,000 photos each day. While I imagine that a photo editor will look at some of the photos prior to publication, it is simply impossible to manually analyze all of these photos. We are working on streamlining our forensic software so that media outlets can process a large number of photos in a relatively short amount of time.</p>
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<span class="qa-start">Q:</span> Why would a magazine or anyone else fake a picture? What do you think their motives usually are? <span class="attrib">Devin Aggeler</span></p>
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<span class="qa-start">Farid: </span> Devin, I think that some magazines are simply trying to create a picture that fits with their story. For example, Newsweek spliced a picture of Martha Stewart's head onto the body of a slim model to accompany the headline "After prison she's thinner, wealthier &amp; ready for prime time". And others just want to sell magazines by splashing a sensational picture onto their magazine's cover ("Brad &amp; Angelina, caught together!").</p>
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<span class="qa-start">Q:</span> What college courses would you recommend for someone interested in someday working in the digital forensics field? <span class="attrib">Josh, Grass Valley, California</span></p>
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<span class="qa-start">Farid: </span> Josh, I would recommend a combination of computer science, applied mathematics, and electrical engineering. Not only will these fields of study provide you with the necessary tools for a career in digital forensics, but they will also provide a broad and generally useful base for future study in many other disciplines. This is particularly important since technology shifts quickly, and you want to create a strong but flexible foundation that allows you to change with technology.</p>
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Father of digital forensics and Dartmouth professor Hany Farid answers questions on photo fakeries and more.

Hany Farid: Expert Q&A





  
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  Kathy is one of only about 100 certified Forensic Anthropologists in the U.S. and Canada. She uses science to solve real-life crime mysteries and to identify remains. But she doesn’t carry a gun.
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  How can you be involved in solving serial murders and not share that kind of magic with the world? You can’t! Kathy is the author of the best-selling Temperance Brennan mystery novels and is a producer/writer for the series, “Bones,” which is based on her novels.
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 Kathy Reichs goes from solving mysteries as a forensic anthropologist to creating mysteries in her Temperance Brennan novels and the TV series "Bones".
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<h2>
 She Couldn’t Even Dissect a Frog
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 Kathy Reichs couldn't dissect a frog in high school, but her favorite "Bones" episode is "gross and disgusting".
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<h2>
 Only for David Duchovny
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 Kathy Reichs gets bamboozled into appearing on an episode of "Bones"... because David Duchovny.
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