MEN who think that using a condom so no semen will be left behind for DNA
analysis, may soon find it harder to escape justice. A new condom
鈥渇ingerprinting鈥� test being developed by Australian forensic chemists could help
provide evidence to convict him.
At the moment, even when a condom is recovered from the crime scene, it can
be impossible to link it to the suspect. Not all rapists ejaculate, so there is
not always semen to analyse. Because most condoms look the same, finding the
wrappers for a particular brand of condom on a suspect usually provides little
evidence. And while forensic scientists have been able to detect common condom
lubricants on vaginal swabs from the victim, this only shows that a condom was
used during a rape without being able to say which kind.
However, in a proof of principle experiment, Garry Lee, Kari Brinch and their
colleagues at the University of Technology in Sydney have shown that most brands
of Australian condoms can be distinguished using nuclear magnetic resonance
(NMR) spectroscopy to analyse the molecular structure of a fragment of condom.
鈥淚t鈥檚 a novel technique,鈥� says James Robertson, director of forensic services at
the Australian Federal Police. 鈥淚t has the potential to be much more
discriminating than some of the earlier techniques.鈥�
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Lee and Brinch took advantage of the fact that although most condoms are made
of latex, a few are made of plastic or sheep caecum, and almost all are coated
with much more than just lubricants. Other coatings include fine powders (to
make them easier to unroll), spermicides, colours and flavourings. These
compounds give most condoms a particular signature in the NMR spectrum.
鈥淧assion Regular and Saturn Regular will look exactly the same,鈥� says Lee.
鈥淏ut you can immediately tell them apart using NMR.鈥� Of the 12 manufacturers
tested, eight could be identified by NMR alone, including the manufacturers that
produce the most popular condoms. Other clues did the rest. For example, Four
Seasons orange flavoured has the same NMR spectra as Nite Glow, but only the
latter glows in the dark. In total, 33 of 38 of the condoms could be
identified.
To simulate condoms that had been flushed down the toilet, the researchers
also analysed them after wiping any lubricant off and soaking them in water for
up to a day. They found that it was still possible to identify 29 of the 38
condoms, says Lee.
Before the test can be used to help investigate a crime, Lee鈥檚 team needs to
find out how condoms vary from batch to batch, and how well the test works on
used condoms. Eventually, Lee hopes to be able to identify all condoms solely by
their NMR spectra, using only a vaginal swab.