New technique to help catch sexual offenders

Sexual offenders hoping to outsmart police by using a condom during their crimes may be out of luck thanks to a technique, being developed at Sheffield Hallam University, that can prove they have had contact with a condom and place them at the scene of the crime.

There has been an increase in the use of condoms by sexual offenders, likely due to both to the risk of sexually transmitted diseases and to prevent the transfer of DNA evidence. The method developed by researchers at the University's Biomedical Research Centre (BMRC) can detect condom lubricant on fingermarks left by a suspect at a crime scene.

This can link a suspect, identified by their fingermark, to the crime in one analysis and can aid police in proving that an offence has taken place. And it is hoped the technique might be used to match lubricant found on a fingermark with residues from vaginal swabs collected from the victim.

Researchers successfully detected lubricant from two widely available condom brands on fingermarks for the first time, and the technique was proven to be successful even on fingermarks left several weeks before analysis.

And the academics hope the technique can eventually be used to identify distinctive lubricants that could indicate a specific condom manufacturer and possibly even a particular brand. This would allow the forensic case to be profiled in an even stronger way.

For the study, researchers used MALDI-MSI (matrix-assisted laser desorption/ionisation mass spectrometry imaging), a powerful technology that can be used to map fingermark ridge patterns.

This research follows on from previous groundbreaking work on the analysis of latent fingermarks by MALDI-MSI that the same researchers pioneered at the BMRC. Dr Simona Francese, from the University's BMRC, said: "Offenders are increasingly aware of forensic issues and it is common now for condoms to be used and removed from the scene of a sexual assault. However, they are less likely to consider the possibility of lubricant transferring onto their fingertips and then into fingermarks left at the scene.

Dr Rosalind Wolstenholme, from the University's BMRC and co-author of the work, said: "If condom lubricant can be detected in fingermarks it would improve the evidence for the prosecution by establishing the assailant's presence at the scene and, crucially, having had contact with a condom. This would enable forensic scientists to provide further support to the evidence in alleged cases of sexual assault."