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different areas of specialization have been developed, and now, as well as medical examiners, there are experts in ballistics , toxicology , serology , and many other disciplines. Early in the 20th century, a French scientist, Dr. Edmond Locard, laid down the basic principle for investigating the scene of a crime: “Every contact leaves a trace.” That is, every criminal leaves something behind at the scene: a weapon; a spent bullet; a print from a finger, hand, or even ear; the track of a shoe; a hair; or a minute fragment of something. And he (or she) also carries something away: powder residue from a gun, a tiny splash of blood, a scratch made by the victim, dust or dirt, or a single fiber from the victim’s clothing. It is the job of the forensic scientist to detect, examine, and analyze these traces to secure evidence for a subsequent trial.

It is essential that the scene of a crime be sealed off as soon as possible to avoid contaminating the site with unconnected contact traces. Ideally, access should be restricted to the medical examiner and the forensic officer and his or her search team.

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FORENSIC SCIENCE