FINGERPRINT TEST TELLS WHAT A PERSON HAS TOUCHED

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.