Bloodstains at Crime Scene Can Tell Age of Victim or Suspect

forensic expert — Scientists have developed a test that can determine whether blood belongs to an adult, adolescent or infant. They expect it to be useful at crime scenes. Monty Rakusen/Getty Images

Thanks to DNA, crime scene blood tests can give a lot of information about victims and assailants. But they've traditionally stopped short of identifying the age of the person(s) in question. In addition, these tests often destroy some or all of the evidence and generally take days or longer to process, leaving investigators twiddling their thumbs while the case grows cold.

To that end, researchers at the State University of New York at Albany decided to use an existing technique known as Raman spectroscopy to analyze blood for details of molecular structure and chemical composition. Since blood changes throughout the lifespan of the average human, the researchers guessed that certain hallmarks would shine light on a person's age. Their findings were published in the June 2018 issue of ACS Central Science .

"This study has particular importance since a person's chronological age cannot be determined through DNA profiling unlike a person's sex and race," they write in the study. "When completed, the developed methodology should allow for phenotype profiling based on dry traces of body fluids immediately at the scene of a crime. The availability of this information within the first few hours since the crime discovery could be invaluable for the investigation."

The team analyzed the blood of 45 human donors. For this initial study, they established three age groups – adults (43 to 68 years old), adolescents (11 to 13 years) and newborns (under 1 year old). Researchers determined the adult samples with more than 99 percent accuracy, and experienced zero errors in regard to the infant samples.

"It is known that human blood differs based on biological sex, chronological age, and health status," they write in the study. "Differentiation of old and young healthy human donors has been shown by comparing levels of alkaline phosphatase (ALP) using a biocatalytic assay." For example, fetal hemoglobin features a different volume of red blood cells and structure when compared to adult hemoglobin. While the test can't say whether the adult is 45 or 52, it can separate an adult bloodstain from that of an adolescent.

Most of the subjects in this initial test were male and all were Caucasian, but the researchers plan to test more female donors and a broader variety of racially diverse people in the future.