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Could crime scene bloodstains reveal a person’s age and the time of the crime?

Forensic assay measures concentrations of a blood enzyme that can distinguish minors from adults and the age of a blood splatter

by Melissa Pandika, special to C&EN
June 13, 2016 | A version of this story appeared in Volume 94, Issue 24

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Credit: Oksana Mizina/Shutterstock
An enzyme-based forensic test for bloodstains could help narrow down the age of the person who left the blood behind, and how long ago they left it.
Photo of bloody fingerprints.
Credit: Oksana Mizina/Shutterstock
An enzyme-based forensic test for bloodstains could help narrow down the age of the person who left the blood behind, and how long ago they left it.

A new forensic blood test could allow law enforcement to determine whether blood at a crime scene came from a minor or an adult and how recently the person parted with it (Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b01169). Jan Halámek of the University at Albany, SUNY, and colleagues focused on alkaline phosphatase (ALP), an enzyme that hits peak levels in the blood during adolescence before decreasing sharply around age 17 for females and 18 for males. The researchers tested 100 samples of human serum spiked with randomly generated concentrations of ALP chosen to match natural enzyme levels found in juveniles and adults. The team determined the ALP concentrations with a known assay that is catalyzed by the enzyme: the conversion of p-nitrophenyl phosphate to p-nitrophenol, a yellow compound that can be measured using spectrophotometry. A statistical test on the measurements revealed that the assay had a 99% probability of differentiating young males from older ones and a 100% probability of differentiating young females from older ones, even after the samples sat on a lab bench near a window for 48 hours to simulate crime scene conditions. The researchers also developed a model based on ALP activity to predict how long blood has been at a crime scene.

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