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Archive for the ‘FINGERPRINTS’ Category




Forensic scientists  would link

sex offenders to condoms

Sexual offenders are increasingly using condoms when committing their assaults, both to reduce the risk of sexually-transmitted diseases, and to avoid leaving their DNA at the crime scene. While an offender might still leave their fingerprints behind, that often only proves that they were at a given location, and not that they were involved in any wrongdoing. Researchers from the Biomedical Research Centre at Sheffield Hallam University, however, have recently developed technology that detects condom lubricant in fingerprints. If a suspect could be tied to a crime scene by their fingerprints, and be shown to have handled a condom at that location – well, they’d have a lot more explaining to do.

The process utilizes MALDI-MSI, or matrix-assisted laser desorption/ionisation mass spectrometry imaging – this allows for the analysis of fragile molecules, that fragment when subjected to more conventional ionization techniques. The Sheffield team previously researched the use of this same technology for mapping fingerprint ridge patterns.

In lab trials, the researchers were able to identify lubricant from two major brands of condoms in fingerprints, some of which were several weeks old. It is hoped that in the future, it might even be possible to match lubricant found in fingerprints to that found in vaginal swabs from victims, or to determine the brand of condom used.

“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,” said Dr. Rosalind Wolstenholme, co-author of a paper on the research. “This would enable forensic scientists to provide further support to the evidence in alleged cases of sexual assault.”

Researchers able to lift fingerprints from clothing

By Paul Ridden

07:29 February 2, 2011

Promising early results from research undertaken by the University of Abertay Dundee and the Scottish Police Services Authority could lead to fingerprint evidence being obtained from clothing, for use in criminal prosecution. Refining an existing technique that’s been used to successfully recover print detail from smooth objects such as glass and plastic, forensic scientists have managed to create a kind of photo negative of fingerprint impressions on fabric. It’s a bit hit and miss at the moment, but even when clear ridge detail isn’t retrieved, the technique could still prove useful to investigators looking for other evidence.

The researchers used a method known as vacuum metal deposition that’s already been used to recover print detail on smooth surfaces like carrier bags, plastics and glass since the 1970s, but has not previously been applied to fingerprint detection on fabrics.

The fabric is placed in a vacuum chamber. Gold is heated and evaporated and spread in a fine layer over the fabric. Heated zinc is then applied, which attaches to the gold layer where the fabric has no fingerprints, leaving the original fabric to show through where contact has been made.

“One way of explaining it is like a photographic negative, where colors show up as their opposites,” said Abertay University‘s forensic sciences teacher and researcher Joanna Fraser. “Here the fingerprint ridges show through as clear fabric, but where there are no ridges we see the distinctive gray color of the metal. Previously it had proved difficult to reveal a clear fingerprint on fabric, but we’ve shown that this is now possible. This is great, but the challenge is to develop this further and confirm its effectiveness.”

The success rate for recovery is still quite low, with only around 20 percent of the public said to consistently leave good ridge detail or indicate target areas for DNA collection due to the presence of sweat. Folks who have drier skin prove to be poor donors, but the technique could still lead investigators to target areas of clothing for DNA procurement and may reveal other useful facts, such as the shape of a hand or an indication of whether a victim was pushed or grabbed.

Paul Deacon, fingerprint unit manager at the Scottish Police Services Authority, said that “an impression of a palm print on the back of someone’s shirt might indicate they were pushed off a balcony, rather than jumping.”

“The research is still in its early stages but we are starting to see results,” he continued. “We have shown that fabrics with a high thread count are best for revealing a print and have recovered identifiable fingerprints on a number of fabrics including silk, nylon and polyester.”

The research paper entitled Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition has now been published in Forensic Science International.

Sourced & published by Henry Sapiecha 

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