The analysis of scent compounds from the palm can predict a person’s sex with more than 96% accuracy – even better than a dog trained to identify individuals and their location – according to a study just published by researchers at Florida International University in the prestigious, open-access journal PLOS ONE.
In criminal investigations, dogs have long been used to reliably identify and track people based on their odor. 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. But while human scent evidence from the field is well established, researchers have made little progress in analyzing human scent profiles in the lab.
Robberies, assaults and rape are all crimes that are often carried out with a perpetrator’s hands, so they have the potential to leave behind valuable traces at a crime scene.
Human odor is a complex mixture of volatile organic compounds (VOCs) secreted from the body that are impacted by genetics, environmental factors and physiological secretions. VOCs are organic compounds, often with high vapor pressures, that are emitted into the environment as gases. A person’s odor in the environment persists because of the constant shedding of the epidermis (outer layer) of the skin; this process leaves epithelial cells in the environment, along with sweat, oils, and other glandular secretions. Many compounds are present in human odors including acids, alcohols, aldehydes, hydrocarbons, esters and ketones.
The new study was led by Prof. Kenneth Furton, a world-leading scholar in forensic chemistry who focuses on trace detection and olfaction, the executive director of the Global Forensic and Justice Center and the university’s chief scientific officer who works in the chemistry and biochemistry.
How did the researchers find this information?
Sixty adults of Caucasian African American and Hispanic race/ethnicity, between the age of 18 and 46 years old volunteered to participate in the study. Furton and his team published their findings under the title “Multivariate regression modelling for gender prediction using volatile organic compounds from hand odor profiles via HS-SPME-GC-MS.”
Until now, human-odor research has shown that scent compounds can reveal a person’s age and racial or ethnic group. With further validation, the chemical and statistical analyses presented in this paper could be used to uncover many details about a potential perpetrator solely through their hand scent profiles.
The Florida researchers used an analysis technique called mass spectrometry to analyze the volatile scent compounds present on the palms of 60 individuals – half of them male and half female. After identifying the compounds in each sample, the team performed a statistical analysis to see if they could determine the individual’s sex based on their profile of scents. They were almost 100% correct.
“This approach to analyzing hand-odor volatiles can be applied when other discriminatory evidence such as DNA is lacking and allow for differentiation or class characterization such as sex, race and age,” they concluded.