Proof's in the print

A new system developed at Purdue University detects trace amounts of explosives, drugs or other materials left behind in fingerprints.

It can also distinguish between overlapping fingerprints left by different individuals - a difficult task for current optical forensic methods.

A team led by R Graham Cooks, Purdue's Henry Bohn Hass Distinguished Professor of Analytical Chemistry, created the system that reads and provides an image of a fingerprint's chemical signature.

Cooks said: 'The classic example of a fingerprint is an ink imprint showing the unique swirls and loops used for identification, but fingerprints also leave behind a unique distribution of molecular compounds. Some of the residues left behind are from naturally occurring compounds in the skin and some are from other surfaces or materials a person has touched.'

Demian R Ifa, a Purdue post-doctoral researcher, said the system can also easily uncover fingerprints buried beneath others.

He said: 'Because the distribution of compounds found in each fingerprint can be unique, we can also use the system to pull one fingerprint out from beneath layers of other fingerprints.