The hope is that a hand mark, which does not have any DNA or fingerprints, could still be used to help identify a perpetrator.
15 key chemicals
“We identified 15 key chemicals, and seven were the most important in differentiating females from males,” study author Dr Kenneth Furton told The Telegraph.
“To date we still cannot say what men and women in general smell like but we can say that they smell different chemically and we are now closer to discovering which chemicals are responsible for that difference.”
Dogs have long been used in criminal investigations to reliably identify and track people based on their odour, but replicating the hyper-sensitive nature of the canine nose with a machine in a lab has proved difficult.
Scientists used a technique called mass spectrometry to analyse the scent compounds present on the palms of 60 people – half male and half female.
Participants were asked to squeeze a piece of sanitised material for ten seconds and their skin secretions were then taken from the absorbent pad and put into a machine.
Odour ‘barcodes’
The scientists found odour “barcodes” which each person possesses that is unique to them and found they were able to pull apart male and female individuals based on the olfactory signature.
“Criminal activities involving robberies, assaults (sexual, simple, or aggravated), and rape are often executed with the use of the perpetrator’s hands,” the scientists write in their study.
“As a result, hands are a focal point of investigations as contributors of trace amounts of evidence that can be deposited on everyday objects through touch interactions.
“There is an exchange of both biological and inorganic material between the perpetrator and the crime scene during these interactions.”
Trace evidence
They add that the interaction and contact between a criminal and victim, or the crime scene, will leave behind trace evidence, but sometimes in quantities too small to help solve the crime.
“Fingerprints and DNA are the biometrics most commonly utilised to identify a suspect or victim of a crime,” the team continues.
“However, these forms of evidence can be found in quantities that are too small to be used, leaving little to no forensic evidence that can be used for prosecution.
“Even in these instances where no physical fingerprint or DNA evidence is found, human scent evidence may still be recovered and used as an individualising feature in an investigation.
“Though previous works have revealed this using an individual’s human scent from either breath or armpit, this study expands on this capability using hand odour which may be of great forensic value.”
According to the study, published in PLOS ONE, the analysis successfully predicted a person’s sex with a 96.67 per cent accuracy rate.
Sexual arousal
Studies are increasingly learning more about the role of human scent and how it may be detected not only by machines but by people too.
One study recently found the chemical makeup of a person’s exhaled breath changes when in a state of sexual arousal and it could be picked up by others around them.
Researchers from the Max Planck Institute of Chemistry found a noticeable spike in three chemicals called indole, cresole and phenol during arousal. There was also a significant drop in the level of CO2 and another molecule called isoprene.
Prof Jonathan Williams, the lead researcher, also found last year that humans have an invisible aura around our bodies which could be cleaning the air we breathe.
A study found that an invisible haze of air-cleansing molecules is produced on human bodies when ozone in the air reacts with oil made by our skin.
