Forensic chemist uses sweat to distinguish individuals at crime scene

May 4, 2018, University at Albany
Forensic chemist uses sweat to distinguish individuals at crime scene
From right: Jan Halámek and students Mindy Hair, Erica Brunelle and Adrianna Mathis. Credit: University at Albany

An average square inch of skin contains 650 sweat glands. That means our bodies leave small amounts of sweat on everything we touch—whether we're making a phone call, eating supper or committing a crime.

Jan Halámek believes investigators can use these tiny, often invisible to their advantage.

Halámek, an assistant professor of Chemistry at the University at Albany, has released a new paper in Analytical Chemistry, which proposes analyzing left behind at a to determine the number of people who were there. The analysis can be used on site at the scene and offer immediate results.

"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," Halámek said. "By combining these concepts, we were able to show that, statistically, sweat left behind at a crime scene can help forensic investigators."

Skin secretions contain a large number of amino acids and metabolites that Halámek says can be targeted once detected on a surface.

His team measures the levels of three of those metabolites—lactate, urea and glutamate. Lactate appears in high concentrations of our sweat and varies greatly based on a person's lifestyle. Urea and glutamate, also highly concentrated, are found in different parts of our sweat. The chances of two people having the same levels of all three metabolites is virtually zero.

To test their analysis, Halámek's team created 25 mimicked sweat samples and took another 25 authentic sweat samples from the forearms of volunteers. Their results indicated that all 50 samples were easily distinguishable.

The next step is to test real crime scene samples.

"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."

Halámek said his analysis currently is unable to match the sweat samples with individuals. This is because metabolites are known to fluctuate over time due to lifestyle changes. For example, some metabolite levels vary with exercise or diet, while others might when a person is sick. However, his lab is beginning to monitor patterns in fluctuations, with a long-term goal of creating a "sweat profile" database.

The paper's first author was UAlbany graduate student Mindy Hair; other student co-authors include senior Adrianna Mathis and graduate student Erica Brunelle. The National Institute of Justice funded the research.

Halámek's new paper adds to a growing portfolio of research that involves non-invasive testing of biomarkers—blood and sweat—to catch criminals.

His team also developed a sweat-based authentication approach for unlocking mobile and wearable devices.

Explore further: Chemist proposes 'sweat analysis' to better secure electronics

More information: Mindy E. Hair et al. Metabolite Biometrics for the Differentiation of Individuals, Analytical Chemistry (2018). DOI: 10.1021/acs.analchem.8b00414

Related Stories

The hidden data in your fingerprints

April 27, 2018

Fingerprints have provided key evidence in countless cases of serious crime. But there are still some situations in which it can be difficult or impossible to recover fingerprints and this can cause a headache for forensic ...

Recommended for you

Synthetic molecule invades double-stranded DNA

November 12, 2018

Carnegie Mellon University researchers have developed a synthetic molecule that can recognize and bind to double-stranded DNA or RNA under normal physiological conditions. The molecule could provide a new platform for developing ...

Scientists bring polymers into atomic-scale focus

November 12, 2018

From water bottles and food containers to toys and tubing, many modern materials are made of plastics. And while we produce about 110 million tons per year of synthetic polymers like polyethylene and polypropylene worldwide ...

New catalyst turns pollutant into fuel

November 12, 2018

Rather than allow power plants and industry to toss carbon dioxide into the atmosphere, incoming Rice University assistant professor Haotian Wang has a plan to convert the greenhouse gas into useful products in a green way.

Nitrogen fixation in ambient conditions

November 12, 2018

Abundant in the atmosphere, nitrogen is rarely used in the industrial production of chemicals. The most important process using nitrogen is the synthesis of ammonia used for the preparation of agricultural fertilizers.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.