Blood stains can reveal age of suspect
A new technique may be a key addition to the CSI toolkit.
Crime scene investigators can learn a lot from a blood stain about the owner’s gender and appearance. But so far, no clues about the age.
Now chemists Kyle Doty and Igor Lednev from the University at Albany in New York have developed a test that can determine the rough age of a person from a blood stain. Moreover, unlike DNA tests which can take weeks and destroy the sample, the new test can be conducted at the crime scene and is non-destructive. The findings were published in ACS Central Science. DNA based fingerprinting, available since the 1980s, zeroes in on ‘markers’. But nailing a suspect requires getting a second sample of their DNA to make the match. Failing that, DNA markers can help detectives narrow down the suspect’s gender, appearance and race. But so far, not the age.
Instead of DNA the new test relies on the blood protein haemoglobin and other chemicals that vary with age. Newborns make foetal haemoglobin which has a different structure to adult haemoglobin and some of the foetal haemoglobin persists into adult life. The researchers used laser-based Raman spectroscopy to probe the structure of haemoglobin, as well as other chemicals that vary with age.
They tested how the spectral pattern changes in infants, adolescents and adults and then developed an algorithm for inferring age. Next they tested their algorithm on dried blood stains taken from 45 volunteers aged less than a year, 11-13, and 43-68. Their analysis was 100% accurate for infants and above 90% accurate for the adolescents and adults. The technique needs further testing; the authors need to sort out how disease or substance abuse might affect the analysis.
But the ability to deliver an approximate age ID within hours of a crime is clearly a powerful addition to the CSI toolkit. As the authors conclude: “The availability of this information within the first few hours since the crime discovery could be invaluable for the investigation”.