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Brain Fingerprinting
Special Report

Crime Solving Science

By Sharon Kay

Forensic science dates back to the 19th century, when fingerprinting and bullet analysis were used as crime-solving techniques. By 1910, French scientist Edmund Locard established the first police crime lab in Paris. Nearly one hundred years later as the role of technology in society continues to expand, judges and juries are increasingly asked to evaluate testimony from forensic science and technology experts. And, as forensic science becomes indispensable to criminal investigations, experts are questioning the reliability of many techniques that were once considered irrefutable.


Fingerprint detection at a crime scene dates back to 1880 Tokyo, where a burglar was apprehended based on fingerprint matching. In 1903, the New York state prison system began to use fingerprinting for identification. The FBI introduced the first computerized scan of fingerprints in 1977. By 1999, instead of using ink, prints could be captured electronically by scanning fingers on a live-scan system and downloading them automatically into the national database.

The average fingerprint contains between 75 and 175 ridge characteristics. Identical prints may appear differently and ridges may be distorted based on the method of print duplication. "Latent" fingerprints -- those lifted from crime scenes -- are often fragments, which show up only after a powder or chemical agent is employed. The outcome may be blurred or distorted, and investigators are unable to match all the ridges. While it is generally believed, though unproven, that each individual has a unique set of fingerprints, people do share some of the same ridge patterns. Critics argue that if a partial print of one person matched a partial print of another, the result could be a false identification. The FBI does not require a minimum number of ridge matches, but judges on a case-by-case basis.

The Polygraph

John Larson and Leonard Keeler designed the portable polygraph in 1921. In 1923, the famous case of Frye v. United States, ruled that the polygraph, then a less complex version of the one used today, was inadmissible in court. When a person takes a polygraph test, they are attached to sensors that measure breathing rate, pulse, blood pressure and perspiration while they answer. In 1998, an appeal to admit the polygraph in court reached the US Supreme Court, but the court ruled that it remain inadmissible because, "To this day, the scientific community remains extremely polarized about the reliability of polygraph techniques."

Polygraph supporters argue that it is accurate when the methodology is strictly monitored, but critics insist that countermeasures can interfere with accurate results. Subjects may try to respond to questions with the same deliberate emotional response. They may self-induce pain as a distraction and a means of overpowering their physiological response to a question. Other methods of "beating" the mechanism are attributed to sedatives and even antiperspirant applied to hands. In 2003, the US National Academy of Sciences issued an assessment of the polygraph, and concluded that, "a variety of psychological and physiological processes, including some that can be consciously controlled, can affect polygraph measures and test results." The report noted that the polygraph could be useful when combined with other techniques for assessing truth.

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Jimmie Ray Slaughter Timeline
Photo of Jimmie Ray Slaughter

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