Blood stains can re­veal age of sus­pect

A new tech­nique may be a key ad­di­tion to the CSI tool­kit.

Cosmos - - Digest -

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”.

CREDIT: OS­CAR ALARCON / GETTY IMAGES

A rough es­ti­mate of the vic­tim’s age can be de­ter­mined from blood at the crime scene.

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