Considering that our skin is covered in sweat glands (on average, 650 sweat glands per square inch of skin), it’s safe to say that we leave a trail of our sweat wherever we go and on whatever we touch. As such, researchers from the University at Albany believe that this “data” can be used to help with crime scene investigations.

“We are looking at two concepts in this paper. First, that each of our skin secretions are different and, therefore, unique to us. Like a fingerprint. Also, we are continuously secreting sweat throughout the day that is being deposited in small amounts as we travel and touch various objects," said Jan Halámek, assistant professor of chemistry at the University at Albany. "By combining these concepts, we were able to show that, statistically, sweat left behind at a crime scene can help forensic investigators."

According to Halámek, included in skin secretions are amino acids and the metabolites lactate, urea and glutamate. Because the metabolites appear in different locations of a person’s sweat and can vary in concentration depending on a person’s lifestyle, it is absolutely unlikely that two people would have the same concentrations of all three metabolites.

To reach this conclusion, Halámek fabricated sweat samples in the lab and also took sweat samples from volunteers. After testing both sets of samples, the team found that all of the samples were distinguishable.

"Investigators tend to overlook the presence of sweat at crime scenes. Our paper is proving it has value," Halámek said. "Without sufficient DNA evidence, which can take days or weeks of analysis, it can be difficult to determine how many people were present at a crime scene. We can quickly gather that information."

Yet, Halámek cautions that the current technique can’t match sweat samples to individuals because metabolites will change over time as lifestyles change — for instance, they will vary with exercise, diet and even illness. Still, Halámek is monitoring these variations and will one day develop a “sweat profile” database.

The research is published in the journal Analytical Chemistry.

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