Shraddha Walkar bones identified using DNA test: What is DNA fingerprinting and how does it help solve crime?

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The origin of DNA fingerprinting

DNA fingerprinting was first developed in 1984 by Alec Jeffreys in the UK, after Jeffreys discovered that no two people could have the same DNA sequence. Within three years of the discovery, the UK achieved the world’s first conviction based on DNA evidence in a case of rape and murder.

Lynda Mann, a 15-year-old girl, had been found raped and murdered in Narbourough, England. This was followed by a similar rape and murder case three years later in the same area. The police arrested one Richard Buckland, who confessed to both crimes. However, when his samples were checked against those found on the dead bodies — they didn’t match. Subsequently, Buckland was exonerated and another man, Colin Pitchfork, arrested and convicted of the murders.

How is DNA fingerprinting done?

Each person’s DNA, except for identical twins, is unique. By analyzing selected DNA sequences (called loci), a crime laboratory can develop a profile to be used in identifying a suspect.

DNA can be extracted from many sources, such as hair, bone, teeth, saliva, and blood. Because there is DNA in most cells in the human body, even a minuscule amount of bodily fluid or tissue can yield useful information. Samples may even be extracted from used clothes, linen, combs, or other frequently used items.

In the Walkar case, DNA from the recovered bones and that of Shraddha’s father has been compared, with the similarity marking close consanguineal relations.

According to a US Congressional Research Service report, DNA evidence is used to solve crimes in two ways:

• If a suspect is known, that person’s DNA sample can be compared to biological evidence found at a crime scene to establish whether the suspect was at the crime scene or whether they committed the crime.
• If a suspect is not known, biological evidence from the crime scene can be analyzed and compared to offender profiles in existing DNA databases to assist in identifying a suspect.

Beyond its accuracy, DNA fingerprinting can also sift through crime scene evidence in different ways, previously unavailable to investigators. For instance, advanced DNA fingerprinting can make separate prints of various individuals even from a sample mixture found at the crime scene — this is of help during gang rape investigations as each perpetrator can be individually identified.

DNA fingerprinting comes to India

By 1988, Lalji Singh, who had been in the UK from 1974 to 1987 on a Commonwealth Fellowship, developed DNA fingerprinting for crime investigations at the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad. Today, Lalji Singh, who passed away in 2017, is known as “the father of DNA fingerprinting in India.”

In 1989, DNA fingerprinting was first used in a case by the Kerala Police. By the early 1990s, the technology had begun to be used for establishing paternity, and to link criminals and identify victims in sensational crimes. From the 2000s onwards, the technology became a staple in rape cases where vaginal swab samples were matched with semen samples from suspects.

Challenges with DNA fingerprinting in India

It is vital to ensure that the DNA of the investigators does not get mixed with that of the victims or the suspects. Thus, picking up samples from a crime scene with sterile tools and storing samples in a proper manner are crucial for the evidence to stand a judicial test.

While India has rules and guidelines regarding this, India’s police forces have a lot of catching up to do with counterparts overseas. While central agencies such as CBI have the expertise to ensure that crime scenes are protected and correct procedure is followed, state police forces are inadequately trained or fully equipped.

“The Aarushi Talwar murder case of 2008 is a prime example. Because the crime scene was not made out of bounds, both police and media trampled all over it. Now the case has no evidence to conclusively establish who killed the 14-year-old girl.” a senior UP Police officer had told The Indian Express earlier.

The problem, however, is not limited to the police. The capacity for DNA fingerprinting in the country itself is lacking. DNA fingerprinting is available only at a few places — Maharashtra, West Bengal, Delhi, Hyderabad and Chandigarh. Advanced practices in the technology are limited to the Centre For DNA Fingerprinting and Diagnostics (CDFD) in Hyderabad.

Some famous investigations where DNA fingerprinting was used

• Shiney Ahuja rape case. Despite his maid’s statement denying that she was raped, in March 2011, Bollywood actor Shiney Ahuja was convicted and sentenced to seven years of rigorous imprisonment. The fast-track court delivering the verdict relied heavily on DNA evidence, in which semen samples from the vaginal swab of the victim matched with the samples obtained from the accused.
• Establishing the identity of suicide bomber who killed Rajiv Gandhi. It was DNA evidence that established the identity of Thenmozhi Rajaratnam who had detonated the bomb that killed ex-PM Rajiv Gandhi and 15 others in 1991. Evidence was gathered from charred flesh and bones found at the site of the explosion.
• Sheena Bora murder case. DNA from some charred bones were discovered in a forest in Raigad, Maharashtra, in August 2015, and matched with the DNA of media entrepreneur Indrani Mukherjea. Until then, she had maintained that her daughter Sheena Bora was away in the USA.