Raman sex test: Saliva samples

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  • Published: Feb 1, 2017
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Raman sex test: Saliva samples

Portable Raman

A portable Raman scanner can analyse saliva, other bodily fluids, and reveal whether or not they come from a male or a female. The system developed by researchers at Albany University, SUNY, State University of New York, USA, may soon be available to scientific support for law enforcement. (Credit: American Chemical Society/Lednev et al)

A portable Raman scanner can analyse saliva, other bodily fluids, and reveal whether or not they come from a male or a female. The system developed by researchers at Albany University, SUNY, State University of New York, USA, may soon be available to scientific support for law enforcement.

Albany chemist Igor Lednev and his colleagues have now released details of a new method for determining a culprit’s sex with almost 92 percent accuracy based on a test of saliva left behind at a crime scene. They are also currently working on a related test for analysing blood stains. About seven years ago, we reported in SpectroscopyNOW on how the same team had developed a Raman spectroscopic method for identifying a fluid sample from a crime scene as being saliva. At the time, we suggested that the identification of traces of bodily fluids found at crime scenes was an increasingly important part of the gathering of evidence especially as DNA testing and data mining themselves become more sophisticated. A conviction or acquittal might pivot on genetic details from a sample, knowing the biological nature of a stain or tiniest sample narrows the focus on such tests leading to stronger evidence. Once aspect of testing that is always a target for forensic work is to determine whether the person from which the sample came is male or female.

Sex revelations

Of course, certainly bodily fluids are obviously sex specific, but not blood, sweat, tears or saliva. However, there are certain characteristics of those substances that might nevertheless reveal the person's sex. The team has once again developed an approach based on non-destructive Raman spectroscopy. They point out that no two compounds produce the same Raman spectrum so an analysis with this technique is like taking a molecular fingerprint. However, unlike conventional fingerprinting the differences between molecular fingerprints can reveal sex.

In a proof of principle, Lednev and his team analysed sixty samples of samples in their laboratory, thirty male and thirty female – using a standard bench-top Raman spectrometer. They probed the data looking for trends and characteristics that differentiated between multidimensional data between the male and the female samples. The team reports details in the American Chemical Society journal, Analytical Chemistry. Team member and graduate student Claire Muro and Luciana de Souza Fernandes also used the same system to analyse other fluids including peripheral blood and sweat as well as vaginal fluid and semen. Although as alluded to above there is generally no forensic doubt as to whether the source of the latter two types of sample are female or male. We reported in 2011 on earlier research from this team that allowed the identification of vaginal fluid.

Sample collaboration

"Our findings have successfully proven the usefulness of Raman spectroscopy in determining sex through saliva," explains Lednev. "We now hope to apply this method using a portable instrument and more realistic samples to simulate crime scene evidence. This could include using traces of saliva deposited on to common substrates." Portable instruments of approximately the size of a hand-held games console are already on the market and could be carried by forensic investigators to a crime scene with little effort. The team hopes to one day see the instrument manufacturers develop a portable "point-and-shoot" Raman device that could be used to quickly and easily identify the type of body fluid, discern whether human or animal origin, and the sex of the source. It might even be possible to ascertain the time of deposition and even the age of the person. Lednev is currently working with the New York State Police Crime laboratory to make the technology practical for investigators and he suggests that it might become available to law enforcement within three to five years.

"After finding what appears to be a biological stain at a crime scene, a forensic investigator would simply need to scan the evidence to collect the necessary data," Lednev explains. "There's no interpretation of the spectra needed. Once the laser hits the sample, they'll get instantaneous answers through automatic software."

Lednev’s latest research adds to the University’s groundbreaking work in forensics. In 2015, we reported on work by another Albany chemist Jan Halámek on identifying sex from fingerprints left at crime scenes using spectroscopy. Lednev and Halámek are now working through several possibilities for collaborating together.

Related Links

Anal Chem 2017, online: "Sex Determination Based on Raman Spectroscopy of Saliva Traces for Forensic Purposes"

Anal Chem 2017, online: "Determining Gender by Raman Spectroscopy of a Bloodstain"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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