With a new analytical technique, a fingerprint can now reveal much more
than the identity of a person. It can now also identify what the person
has been touching: drugs, explosives or poisons, for example.
Writing in Friday’s issue of the journal Science, R. Graham Cooks, a
professor of chemistry at Purdue University, and his colleagues describe
how a laboratory technique, mass spectrometry, could find a wider
application in crime investigations.
The equipment to perform such tests is already commercially available,
although prohibitively expensive for all but the largest crime
laboratories. Smaller, cheaper, portable versions of such analyzers are
probably only a couple of years away.
In Dr. Cooks’s method, a tiny spray of liquid that has been electrically
charged, either water or water and alcohol, is sprayed on a tiny bit of
the fingerprint. The droplets dissolve compounds in the fingerprints and
splash them off the surface into the analyzer. The liquid is heated and
evaporates, and the electrical charge is transferred to the fingerprint
molecules, which are then identified by a device called a mass
spectrometer. The process is repeated over the entire fingerprint,
producing a two-dimensional image.
The researchers call the technique desorption electrospray ionization,
or Desi, for short.
In the experiments described in the Science paper, solutions containing
tiny amounts of various chemicals including cocaine and the explosive
RDX were applied to the fingertips of volunteers. The volunteers touched
surfaces like glass, paper and plastic. The researchers then analyzed
Because the spatial resolution is on the order of the width of a human
hair, the Desi technique did not just detect the presence of, for
instance, cocaine, but literally showed a pattern of cocaine in the
shape of the fingerprint, leaving no doubt who had left the cocaine
“That’s an advantage that this technique would have,” said Bruce
Goldberger, professor and director of toxicology at the University of
Florida who runs a forensics laboratory that helps medical examiners and
law enforcement. Dr. Goldberger was not involved in the research.
The chemical signature could also help crime investigators tease out one
fingerprint out of the smudges of many overlapping prints if the person
had been exposed to a specific chemical, said Demian R. Ifa, a
postdoctoral researcher and the lead author of the Science paper.
Prosolia Inc., a small company in Indianapolis, has licensed the Desi
technology from Purdue and is already selling such analyzers as add-ons
to large laboratory mass spectrometers, which cost several hundred
thousand dollars each.
Prosolia has so far sold about 70 analyzers, said Peter T. Kissinger,
the company’s chairman and chief executive. The most sophisticated
$60,000 version that would be needed for fingerprint analysis went on
sale this year.
However, fingerprints are not the main focus for Prosolia or Dr. Cooks.
“This is really just an offshoot of a project that is really aimed at
trying to develop a methodology ultimately to be used in surgery,” Dr.
If a Desi analyzer can be miniaturized and automated into a surgical
tool, a surgeon could, for example, quickly test body tissues for the
presence of molecules associated with cancer. “That’s the long-term aim
of this work,” Dr. Cooks said.
In unpublished research, the researchers have successfully tested the
method on bladder tumors in dogs.
Prosolia is collaborating with Griffin Analytical Technologies, a
subsidiary of ICx Technologies, on a Desi analyzer that works with a
portable mass spectrometer. That product is probably a year or two away
from the market, Dr. Kissinger said.
As it becomes cheaper and more widely available, the Desi technology has
potential ethical implications, Dr. Cooks said. Instead of drug tests, a
company could surreptitiously check for illegal drug use by its
employees by analyzing computer keyboards after the workers have gone
home, for instance.
Copyright 2008 The New York Times Company. Reprinted from The New York
Times, Science, of Friday, August 8, 2008.