Right temperature vital for blood in forensics

Bloodstains collected from a crime scene are essential sources of evidence in investigations. But a recent study has revealed that to get accurate evidence from bloodstains, it is essential that a specific temperature is maintained according to the type of blood antigens, of which there are three — A, B and O. Shortcomings in maintaining the blood at the right temperature can give negative results, which can create a hurdle in forensic investigations, the study said.

The Directorate of Forensic Science Laboratories, Mumbai and Regional Forensic Science Laboratory, Nashik have revealed this in their recently concluded two-year-long study. Its results were recently published in the Journal of Pharmaceutical, Chemical and Biological Sciences.

In a crime scene investigation, in the absence of fresh blood, dried bloodstains are taken for analysis. In these dried bloodstrains, the red blood cells are all haemolysed, which involves a process of breaking down of the red blood cells in blood. These haemolysed cells retain their property for a considerable period of time. This becomes an important marker in forensic casework.

To reduce the effects of temperature and ageing on bloodstains, many samples were kept in five different temperatures and studied: at room temperature, 4 degrees C, 37 degrees C, 56 degrees C and 110 degrees C.

“Our study shows that A and B antigen strains lose antigen activity after about two years while ‘O’ antigen stains lose activity after about a year,” said U.K. Kulkarni from the Regional Forensic Science Laboratory.

“It shows that if blood antigens are kept at a higher temperature, they loses their accuracy. So, it is inevitable to store the blood at a lower temperature to retain its accuracy. Failure to do so can give negative result affecting crime investigation. North Maharashtra (as it has a higher temperature) should be more careful in storing bloodstains,” Mr Kulkarni added.