[tt] NYT: Fingerprint Test Tells What a Person Has Touched

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Fingerprint Test Tells What a Person Has Touched
New York Times, 8.8.8
http://www.nytimes.com/2008/08/08/science/08finger.html

By KENNETH CHANG

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 the fingerprints.

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 behind.

"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. Cooks said.

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.
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