Updating Fingerprint Technology
What do you get when you cross an organic chemist with the U. S. Secret Service?
In at least one case, such a partnership has resulted in a means of developing fingerprints at crime scenes that's less damaging to evidence, more sensitive and less expensive for law enforcement agencies. The class of chemicals the team ultimately fingered, known as indanediones, recently received a U. s. patent, and a European company has obtained a non-exclusive license to the technology.
This unusual crime-fighting alliance was born several years ago when federal agents appeared unannounced at the laboratory of Madeleine M. Joullié, Class of 1970 Professor of Chemistry. They thought the organic chemist might be just the answer to modernizing the dusty old art of fingerprinting.
"Often we were speaking entirely different languages," Dr. Joullié said of her unlikely detour into work supported by the national Institute of Justice. "I'd go to law-enforcement conferences where nobody else understood me and I didn't understand anybody else."
Despite the cultural gulf separating them, Dr. Joullié and her colleagues in the Secret Service managed a balancing act in more ways than one. Methods used to detect fingerprints must be gentle and sensitive--the smudge left on a surface by a passing finger contains, on average, just one millionth of a gram of amino acids, fatty acids, glycerides, urea and salts--and yet inexpensive enough to be dusted on evidence at crime scenes. Indanediones appear to fit the bill better than any of the various fingerprinting compounds now available.
Despite other technological advances in law enforcement, the materials used in this staple of crime-scene investigation have remained remarkably low-tech over the years. While various alternatives exist, the fingerprinting chemical most used by law enforcement agencies the world over is a 1950s-era compound called ninhydrin.
Another fingerprint-finding compound now used by some police departments, diazaflourenone, comes in at roughly $40 a gram, a real budget buster for most police departments. The indanediones developed by Joullié can be produced for a fraction of that cost via a relatively straightforward, reliable sequence of reactions.
Low cost isn't indanediones' only advantage. When combined with the amino acids in a fingerprint, indanediones' heightened sensitivity caused them to glow even more brightly than the pricey diazaflourenone. Inadanediones are also significantly easier to use.
"To avoid thermal decomposition of evidence, diazafluorenone prints must be developed with a carefully timed application of a high-temperature, dry-heat system," Dr. Joullié said. "In the case of indanediones, only steam heat is necessary, which does not damage the evidence."
Dr. Joullié was joined in the development of indanedione fingerprinting compounds by Diane Hauxe and Olga Petrovskaia, both of whom received their doctorates from Penn, and Bruce Taylor, formerly a postdoctoral researcher at Penn. Colleagues at the Secret Service included forensic chemists Anthony Cantu and Robert Ramotowski.
Almanac, Vol. 47, No. 26, March 20, 2001