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Brain Fingerprinting
Special Report

Crime Solving Science

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Bullet Lead Analysis

Developed by the FBI in the 1960s, "compositional analysis of bullet lead" (CABL), measures the likelihood of a chemical match between crime scene bullets and those found in the possession of a suspect. The technique is often used when a bullet is found at the crime scene, but no gun is recovered (another ballistic analysis technique involves matching marks left on a bullet with those made by distinct gun barrels.) If a suspect possesses bullets, law enforcement officials compare the chemical compositions to determine whether they match the bullet found at the crime scene. But a new report published in 2004 by the US National Academies' Board on Chemical Sciences and Technology, a private non-profit organization that provides scientific advice to the federal government, states that some lead bullet analysis methods are flawed. Incriminating results may have contributed to previous murder convictions, including that of Jimmy Ray Slaughter.

The report noted that a type of analysis known as "chaining" was particularly inconsistent. The technique involves comparing trace elements of bullets within a particular box to those elements found in the bullet at the crime scene. However, bullets sold in one package are not necessarily produced from the same batch of melted lead, and alternately, bullets from a single batch of lead make it into many different boxes.

DNA Profiling

DNA profiling is a method of identifying an individual by the unique characteristics of that person's DNA taken from saliva, skin tissue, blood, hair, or semen found at crime scenes. DNA technology helps convict criminals or exonerate suspects. First developed in England in 1984, by Dr. Alec Jeffreys, it is now widely used by police, prosecutors, defense counsel, and courts in the United States and elsewhere in the world. Though DNA profiling has been proven highly accurate, discrepancies remain in how many matching chromosomes of a particular gene are tested. In some cases, DNA testing has been proven inaccurate when a suspect is considered guilty based on only a partial match. Though the FBI is reported to test 13 different types of matches, which significantly reduces the chance of a mismatch, state and local laboratories do not always test for the same compatibility.

In some cases, especially "cold cases" involving DNA from old samples, the DNA may degrade and becomes less reliable for accurate matching. In other cases, DNA may be contaminated at crime scenes by law enforcement personnel or by natural environmental elements. DNA can also be mishandled and contaminated in labs where it is analyzed.

Brain Fingerprinting

Brain fingerprinting is a technique that involves brain wave monitoring with an electroencephalograph (EEG) machine. The waves denote whether potentially incriminating information is stored in a person's memory. The technique, based on monitoring a scientifically established brain wave response known as the P300, registers a person's recognition or lack of recognition of intimate details related to a crime. Developed 20 years ago by Dr. Larry Farwell, the method is slowly making its way into the criminal justice system.

It has yet to be determined whether brain fingerprinting tests will be admissible in court, and some critics question the methods of eliciting the P300. However, brain fingerprinting results recently contributed to the successful appeal of a man convicted of murder in 1978. Along with other newly discovered evidence, brain fingerprinting results were accepted into evidence, and the man ultimately obtained a new trial. As the technique gains recognition, new cases may set precedents for both expanding and refining the methodology. It is still early to judge whether brain fingerprinting will compete with more acceptable forensic tools, but like other crime solving techniques it will continue to face stringent scientific scrutiny and provoke scientific and legal debate.

Sharon Kay is the INNOVATION series Science Editor. She is also a freelance science writer and producer in New York City. Her work has appeared on public television, in the American Museum of Natural History, and in THE BOSTON GLOBE.

Photo of a DNA profile.
DNA profiling is a method of identifying an individual by unique characteristics of that person's DNA found at crime scenes in the form of saliva, skin tissue, blood, hair, and semen.
Brain Fingerprinting results recently contributed to the successful appeal of a man convicted of murder in 1978.

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