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Last month, Delhi Police recovered bones from the Mehrauli forest area in connection with the Shraddha Walkar murder investigation. DNA testing conducted on the bones — parts of the jaw, pelvis and lower limb — has now confirmed a positive match with Shraddha’s father. Further examination of the bones will be conducted to ascertain the cause of death and time period, sources say.
Given that Walkar’s body was allegedly dismembered and disposed of by her live-in partner Aaftab Poonawala, DNA evidence is crucial in this case. The Indian Express explains what exactly is DNA fingerprinting and how it helps authorities solve crime.
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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.
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:
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.
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.
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.
