Crime-busting chemical imaging

Engineers at Imperial College London have designed a method of collecting fingerprints with their chemical residue, and keeping them intact for future reference.

As well as potentially detecting the diet, race and sex of a suspect from their fingerprint, the technology could identify traces of substances that people have come into contact with, such as gunpowder, drugs and biological or chemical weapons.

All fingerprints contain a few millionths of a gram of chemical fluid that is often distorted or destroyed in traditional fingerprinting techniques. The scientists found that by using commercial gelatine-based tapes to lift prints, they can be transported safely and intact to the laboratory for chemical imaging analysis.

In the laboratory, the prints can be analysed in a spectroscopic microscope, where infrared rays excite the sample to identify individual molecules within the print to give the composition of the chemical. This information is then processed by an infrared array detector, originally developed by the US military in smart missile technology, which maps the residue and returns a chemical photograph of the sample.