The use of volatile organic compounds (VOCs) from human scent as forensic evidence has been established, particularly with canines in crime scene investigations. However, the laboratory analysis of human VOC profiles has been limited. In a groundbreaking study conducted by researchers at Florida International University (FIU), it has been determined that an individual’s biological sex can be accurately confirmed through the analysis of their hand odor. This innovative approach has the potential to significantly assist forensic investigations, especially in cases where traditional biometric indicators such as DNA and fingerprints are limited or non-existent. Published in the renowned open access science journal PLOS ONE, this research represents a significant advancement in the field of forensic science.
Hand Odor as a Potential Forensic Tool
Criminal activities often leave traces, and the hands of perpetrators can contain valuable evidence that can aid in investigations. By analyzing hand odor, forensic investigators can gain crucial insights into the identification and tracking of individuals involved in crimes such as robberies, assaults, and rape.
Human odor is a complex mixture of volatile organic compounds (VOCs) that are secreted from the body and influenced by genetics, environmental factors, and physiological secretions. VOCs are organic compounds that exist as gases and have high vapor pressures. The persistence of a person’s odor in the environment is attributed to the constant shedding of the outer layer of the skin, which leaves behind epithelial cells, sweat, oils, and other glandular secretions. Human odors contain various compounds, including acids, alcohols, aldehydes, hydrocarbons, esters, and ketones.
Collecting Hand Odor Samples and Analyzing VOCs
Every contact leaves a trace, and this principle forms the foundation of forensic science. When an individual touches an object, they inevitably leave behind a part of themselves, including their unique odor. Expanding on this principle, the research team at FIU collected hand odor samples from 60 volunteers, from Caucasian, African American, and Hispanic backgrounds, aged between 18 and 46 years, comprising an equal number of men and women. Using state-of-the-art instruments commonly found in forensic toxicology and chemistry laboratories, such as gas chromatography/mass spectrometry (GC-MS), were used to analyze the VOCs responsible for hand odor. The researchers employed a technique called Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) to extract and analyze the VOCs present on the palms of the participants.
Predicting Gender through VOC Analysis
After identifying the compounds in each sample, the team conducted a statistical analysis to determine whether they could accurately predict an individual’s gender based on their scent profile. The researchers utilized supervised dimensional reduction techniques, including Partial Least Squares-Discriminant Analysis (PLS-DA), Orthogonal-Projections to Latent Structures Discriminant Analysis (OPLS-DA), and Linear Discriminant Analysis (LDA), to interpret the VOC signatures and predict gender based on the hand odor profiles. The results were remarkable, with the models showing clear clustering and discrimination between male and female subjects. The LDA model achieved an impressive accuracy rate of 96.67% in classifying the gender of the individuals.
Beyond Forensic Applications
While the primary focus of this study lies in the realm of forensic investigations, the implications of this research extend far beyond the field. According to statistics from the FBI, approximately 72% of crimes are committed by men, while women account for around 28% of the total. The ability to confirm biological sex through hand odor analysis holds the potential for various non-forensic applications in the future.
The Future of Hand Odor Analysis
This pioneering research conducted at FIU opens up exciting possibilities for the integration of hand odor analysis into forensic investigations. As a complementary tool to the remarkable olfactory capabilities of detection canines, this technique provides investigators with an additional means to bring justice to the victims of crime. By leveraging advancements in analytical chemistry and machine learning, researchers like Chantrell Frazier and her team at FIU are paving the way for more effective and efficient forensic investigations.
Conclusion
The recent research conducted at FIU has established hand odor analysis as a reliable method for confirming an individual’s biological sex. By harnessing the power of volatile organic compound analysis and employing innovative data analysis techniques, FIU researchers have achieved an impressive accuracy rate of over 96%. This breakthrough has the potential to significantly impact forensic investigations, particularly in cases where traditional biometric indicators are limited or unavailable. The collaboration between forensic science and chemistry at FIU showcases the immense potential of interdisciplinary research in advancing the field of forensic sciences. As this research continues to evolve, the integration of hand odor analysis alongside existing forensic methodologies promises to enhance the pursuit of justice and bring solace to victims of crime.
Study Reference: Frazier CJG, Gokool VA, Holness HK, Mills DK, Furton KG (2023) Multivariate regression modelling for gender prediction using volatile organic compounds from hand odor profiles via HS-SPME-GC-MS. PLoS ONE 18(7): e0286452. https://doi.org/10.1371/journal.pone.0286452
Photo credit: Eduardo Merille, Florida International University and Creative Commons
