A new method can quickly but accurately narrow down whether someone is an adult or a juvenile based on fluids left behind.

Picture of swabs with blood samples for DNA testing

Scientists have discovered a way to figure out a suspect’s age range based on blood found at a crime scene, like the swabs seen here.


Chemists at the University at Albany, SUNY, have described a new method for quickly but accurately determining a person’s age range based only on a blood sample. The test could one day be used to help narrow down suspects in a crime scene investigation as easily as getting results from a glucose or pregnancy test.

“I hope it will change [and] accelerate the investigation, so you can know right away what is happening,” says Jan Halámek, co-author of the paper, which was published in May in Analytical Chemistry.

Traditional DNA analysis can take up to 72 hours and carries no reliable information about a person’s age. So Halámek and his team focused on levels of alkaline phosphatase (ALP), an enzyme found in blood, to determine age.

In adolescence, active bone growth releases ALP, but when people reach adulthood, bone growth slows and ALP levels begin to plummet. This threshold is generally around age 17 for women and 18 for men. That means the method can help differentiate between juveniles and adults, groups who are treated differently by the legal system.

Bloody Tools

The team started with human serum, a commercially available substance similar to real human blood that is easier to acquire than the real thing. Halámek and his colleagues then spiked a hundred serum samples with different concentrations of ALP designed to mimic those found in healthy adults.

Twenty-five samples with high ALP levels represented young females, while 25 samples with low levels represented older females. The team tested the same ratios for young and old males.

Using a procedure called a biocatalytic assay, the researchers looked for specific chemicals created by the enzyme’s activity. That allowed them to determine ALP levels, and thus age ranges, with a success rate of nearly 100 percent. Even after leaving the samples on a lab bench for 48 hours to simulate the time that may pass at a crime scene, the results were still just as accurate.

George Schiro is lab director and forensic scientist at Scales Biological Laboratory in Mississippi. He says the research for the project is good, but he notes that the experiment was carried out under controlled conditions. Many crime scenes aren’t found until more than two days after an incident, so by the time first responders actually find blood at a site, samples may be too diluted for the ALP test.

Additionally, he says, the high-quality serum samples Halámek and his team used for the experiment aren’t real human samples, and there might be a minimum amount of actual blood needed to complete the test.

“There’s more research that has to be done before it’s going to be useful for any type of field investigation,” Schiro says. But assuming it makes it into the field, the test may be helpful if investigators can then combine resulting age ranges with a suspect’s other characteristics, like eye or hair color, he adds.

Halámek says his team is still working on the chemistry of the project. The next step is to study different components in the blood to see if they relate to variables like gender and ethnicity. The team is also working to narrow down the age range to within a span of two or three years.

Until then, the investigation is ongoing.


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