India's first DNA bank to ease identification of criminals in court

Clues like blood or hair can either link a suspect with the crime scene or rule him out. Deoxyribonucleic Acid (DNA), the double-strand bearer of genes, extracted from biological evidence, can never lie as no two people-barring twins-have identical DNA.

What is more, it is easier to obtain than the classic fingerprint. There is, however, a legal block. When the prosecutor asks a judge to convict a person because the probability of his being the offender, based on DNA evidence, is beyond reasonable doubt, the defence retains the right to ask how high this probability is.

Forensic scientists often isolate the allele, or a rung on the DNA, to prove a subject's uniqueness. The genetic patterns obtained can determine whether two DNA samples are from the same person, related people or non-related people.

Scientists use this to get the probability of a match. This is where the problem arises. How unique is the information on the allele? A suspect would be more readily nailed if his DNA profile occurred, say, once in five million people than if it occurred in one out of 5,000 people.

Now, with the set-ting up of a DNA bank in Kolkata, this probability is easier to determine. The bank can help the legal system relate genetic evidence to the population and put a figure on the likelihood of the suspect being the offender.

{mosimage}Set up recently by the Central Forensic Science Laboratory (CFSL) on the directive of the Union Home Ministry, the bank has DNA samples of over 8,000 individuals from 107 of the country's 5,834 population groups, including 25 castes, 25 tribes and 57 occupational categories.

"We chose the communities," says V.K. Kashyap, CFSL director-principal and the project in charge, "in the same way as constituencies are selected for poll analyses, with highest swing zones getting maximum preference."

CFSL, which plans to collect around 1.5 lakh samples, has opted for mitochondrial DNA inherited from mothers against the regular (nuclear) DNA that comes from both parents.

This is useful in tracing maternal lineages and could aid in solving hospital baby-swapping cases. Markers on the Y chromosome-which pairs with the X chromosome in males-will also be studied.

Transmitted from the father to his sons, it is a powerful measure of paternal relatedness across geographical frontiers and generations. Also in the offing is the use of the DNA bank in specific drug testing.

The CFSL databank could be the be-ginning of an Indian version of the FBI's Combined DNA Index System in the US, which allows agencies to match DNA profiles among a pool of banks or even to verify life insurance and social welfare claims. In fact, the CFSL project was initiated on international pressure.

Forty-three countries have legislated to make collection of DNA samples from convicts compulsory and 26 nations have agreed to create a "DNA highway", standardising methods for analysis. In India, the Department of Biotechnology has set up task forces for standards and for formulating the enabling law.

The wide applications apart, the primary focus of the database will be to validate forensic evidence, providing a new blueprint for criminal trials in the country.

Sumit Mitra

Source: indiatoday.intoday.in