Sep 03, 2008

"Smart" Fingerprint Technology

Forensic testimony based on fingerprint comparison is a familiar part of many criminal trials. Based on the generally-accepted principle that no two people (even twins) have identical fingerprints, experts often tie suspects to crimes through providing testimony that the suspect's fingerprint matches the prints found at a crime scene.

Now, with the help of a new laboratory technique, forensic experts may be able to "read" fingerprints and identify substances embedded in them. The laboratory technique consists of a process called "mass spectrometry," and as a result, fingerprints may serve as suspects' "chemical signatures".  For example, an expert may be able to testify that "the person who left this fingerprint had been touching cocaine (or a poison, or an explosive)."  Such testimony would do more than tie a suspect to a crime scene: It would also help to explain the suspect's motive for being at the scene. For instance, assume that Bob is charged with murder-by-poison. At trial, forensic expert testifies, "I found traces of the same poison in fingerprints found at the crime scene, and in my opinion, the fingerprints are identical to those of Bob." Such testimony does more than prove that Bob was at the crime scene -- it also helps to show how Bob committed the murder.

Because of popular TV crime shows, such as C.S.I., jurors have generally come to expect and be favorably impressed with forensic evidence. "Smart" fingerprints, which may indicate not only who was at a crime scene but also their purpose for being there, is a potentially powerful prosecutorial tool.