Background: The Noida double murder in May 2008 highlighted the intriguing socio-legal realities facing middle-class India as well as the gross ineptness of the local police. The case proffered a plethora of forensic clues that should have been adequate for solving the crime(s). While the popular discourse may have unduly emphasized the moral corruption of the police force as the reason d’être, gaping holes in the investigation were ultimately a manifestation of inadequate training and resources. In November 2013, Nupur and Rajesh Talwar were convicted of murdering their daughter Arushi and the household help Hemraj Banjade. Interestingly, a blood-soaked handprint had been found on the terrace wall, was photographed and some samples collected as well. However, thorough analysis of the hand print could never be performed as it was washed away by rains in the intermittent. In the age of 24-hour news channels where two-minute sound bytes are the norm rather than the exception, much has been made about the importance of the hand print. The movie Talvar released in October 2015 did its part of invoking the hand print as a vital piece of the puzzle that was lost thanks to the negligence of the police. In order to understand how vital the hand print really was, one first needs to learn about the advances in modern forensic analysis and especially how certain molecules provide unique signatures of each individual.

Emergence of DNA as the Magical Identifier: Historically, blood groups held sway as a quasi-unique identification tool in the context of criminal cases with limited number of suspects. Blood groups refer to the presence of specific arrangement of sugar molecules on the surface of red blood cells (in the blood). However, the fact that these arrangements (and therefore the blood groups) are shared by large number of people even in a small population means that it can never be completely relied upon for providing conclusive evidence on the association of a specific person with the crime scene. The blood soaked hand print in the Noida double murder case is thus only superficially related to blood groups and blood typing. Instead, the uniqueness of an individual is now accepted as being best represented by certain traits of their DNA. The latter in turn can be easily extracted from blood or other bodily substances such as hair follicles, skin cells and semen thereby making DNA analysis the most promising forensic tool. DNA is widely understood as being the repository of our genetic information, that stores the information necessary for initiating and guiding all life processes. Since the discovery of the double helical structure of DNA by James Watson and Francis Crick in 1952, we have come a long way in our understanding of DNA as the fundamental genetic material. In comparison to other biomolecules that make up our body, DNA is relatively easier to visualise as a (very) long thread (super)coiled into a dense bundle and packed inside the nucleus of cells. The successful completion of the Human Genome Project has provided unprecedented insight into the complex layers of genetic information stored in our DNA. In a crude analogy linking all of our genetic information to the printed information stored in the college library, each cell in our body could be considered as a book and each chapter in the book would correspond to the nucleus which houses the genetic material. The letters that make up the words on a line in a page of each chapter of our symbolic book could be considered analogous to the much-known “bases” in DNA namely A, T, G and C. These moieties are also known as nucleotides and are the building blocks of the long polymeric DNA that is present in each of our cells. Variations in the sequence of these building blocks from one person to another, could ultimately be held responsible for the diversity of traits in humans. Interestingly enough, the sequence variations of nucleotides also termed sequence polymorphism only amounts to around 0.3% of the human genome. That adds up to differences in nearly 10 million nucleotides and it is in these variations that the “fingerprint” of an individual can be found. Such DNA sequences that are used for forensic identification do not provide any information on any personal trait such as their height, eye color, hair color, blood sugar or cholesterol levels. Within the different forms of DNA sequence variations, length polymorphism is most easily tracked and now forms the basis of state-of-the-art DNA forensic strategies. One of the first methods that relied on length polymorphism was restriction fragment length polymorphism or RFLP. RFLP relied on the differences in lengths of specific DNA sequences between individuals. The unique site of DNA that exhibits such length polymorphism is termed a locus (plural: loci) and can be approximated to a line on a page as per our book symbolism. RFLP was mainly based on the application of one of the bedrock DNA technologies of late 20th century, namely restriction endonucleases. These nucleic acid ‘cutting’ enzymes would only perform their action at well-defined DNA sequences rather than being indiscriminate as most nucleases were known to be. The ‘cutting’ or breakage of DNA at precise locations would in turn produce a set of well-defined fragment lengths. The pattern of fragment lengths hence produced would become the fingerprint and a simple comparison of patterns across samples could be used for matching or exclusion.

Modern DNA Forensic Analysis: The RFLP method though successful was tedious and required high amounts of the source DNA to be analysed effectively and eventually gave way to the more robust process called short tandem repeat or STR analysis. STR analysis exploited the presence of variable number of nucleotide repeats at specific locations or loci of the human genome. An example of an STR at a particular locus is 5’-(GATA)(GATA)(GATA)(GATA)-3’ where the 5’ and 3’ refer to the two ends of DNA and the nucleotides within parentheses corresponding to the STR. In this example, the STR is said to have 4 (four) repeating units. A second person may have a different number of repeating units (say, 6) at that locus. The United States Federal Bureau of Investigation (FBI) assesses the repeating units at 13 separate loci, that have been deemed sufficient to create a pattern that would uniquely identify each and every individual on the planet! The widespread success of STR-based DNA forensics in the late 20th century was facilitated by the emergence of two technologies involving DNA namely capillary electrophoresis and polymerase chain reaction (PCR). Capillary electrophoresis provided a sophisticated and high-throughput method of visualising differences in lengths of DNA. PCR enabled the amplification (or increase in amount) of source DNA being analyzed, thereby revolutionising the ability to work with trace amounts of biological samples. The convergence of these two technologies enabled the extraction and analysis of specific short tandem repeat regions of DNA present in cells that could be collected from crime scenes and compared to the STR of individuals associated with the crime (and/or) scene. The pattern of short tandem repeating unit lengths is termed as the STR profile and appears as a string of alpha-numeric characters. Thus, the string:16-16;17-17;18-21; 22-12; 14-28; 30-14; 16-12; 13-11; 14-9; 9-11; 13-6; 6-8; 8-10 represents the number of short tandem repeats for a person across 13 loci that are specifically used for forensic identification. The pair of numbers separated by the hyphen, are termed alleles and represent the STRs corresponding to the same locus but on two separate chromosomes. Reasons for variation of STRs at the same locus across the two chromosomes are not entirely understood. For that matter, reasons for the variation of STRs from one person to another are not straight forward, as the corresponding DNA segments do not code for any proteins. Comparison of the alpha-numeric strings corresponding to evidence and suspect(s) leads to two main scenarios: (1) Exclusion (or no match) and (2) Inclusion (or match). Exclusion refers to a clear mismatch in the numeric string across several loci. ‘How many’ mismatches constitute a true exclusion depends entirely on the probability of occurrence of the STR numbers at the corresponding loci. The scenario of inclusion is really the one sought after by investigating agencies. The numeric string representing DNA from the crime scene would most certainly contain numbers belonging to the numeric string of a suspect said to be associated with the scene (and possibly the crime). The oft-heard statement, ‘there is 1 in a trillion chance that DNA from the crime scene belongs to someone other than the suspect,’ is a firm confirmation of inclusion. The odds of matching are deduced from the probability of occurrence of the specific number of repeats at each locus. The existence of repeat sequences at loci across the human genome as well as the variation of such repeat sequences in selected populations is the subject of an entire domain of research.

Scenarios in the Talwar Case: Coming back to the blood soaked handprint in the Talwar murder case, proper evidence collection and storage could have gone a long way in resolving the crime. For one, Rajesh and Nupur Talwar’s presence on the terrace would be confirmed from a match of STRs at just 7 loci, the probability of such match being approximately 1 in 44 million which is much more than the population of Delhi and the Noida area. Conversely, the case against the parents would be weaker, in case their STRs were not found in the blood evidence collected. While this would not necessarily rule out their presence on the terrace at the time of the crime, the exclusion would make it harder to nail them as active participants. Apart from these clear depictions of inclusion or exclusion, there exists the very real probability of a completely muddled ‘in-between’ scenario where Rajesh and Nupur were complicit in the murder of Hemraj who either by himself or with the help of other accomplices had murdered Arushi. As far-fetched or hypothetical as this may seem, DNA from the blood-soaked handprint would have gone a long way in bringing us closer to this or any number of other scenarios that may have played out. In this regard, the blood-soaked handprint symbolises other critical pieces of evidence such as the golf club suspected to have been the murder weapon and the whiskey bottle found on the dining table when Arushi’s murder was first discovered. Each of these pieces of evidence was mishandled and forensically damaged highlighting the systemic weaknesses of the investigative process.

The Hurdles: Unfortunately, the confounding outcome of this case may not have been much different in nearly any other state of India. The DNA Profiling Bill of 2007 is awaiting budgetary approval. This piece of legislation would make it possible for creation of a nationwide database enabling the legal recognition of DNA fingerprinting evidence. While few high-profile instances such as the N D Tiwari paternity case and the Bhanwari Devi murder investigation have relied on key DNA forensic analysis, the nationwide outlook remains bleak. On a related note, for a country of India’s size, there exist a pathetically small number of training institutes for forensics in general and DNA forensics in particular. Forensic science programmes  need to be calibrated against the genuine demand that it’s graduates would encounter. Similarly, the over-reliance on expensive imported technologies needs to be challenged and solutions unique for the ethnic diversity of India need to emerge. Lack of appreciation of state-of-the-art forensic sciences does not imply DNA forensics alone. Rajesh Talwar was said to have had alcohol the night before the murders. Other suspects (some named and others not so) were said to have been under the influence of narcotic substances. Blood from the handprint would have been immensely useful for the detection of trace quantities of these substances. In the end, the much abused orthodox approach of selective interpretation of testimony and circumstantial evidence may have led to a miscarriage of justice in the Noida double murder case.

The truth, it is said, can never really be known. It can only be pursued. The blood-soaked hand print would have gone a long way in that pursuit.

Prof. Bhaskar Datta

Prof. Bhaskar Datta

Assistant Professor at IIT Gandhinagar, Chemistry and Biological Engineering

Prof. Bhaskar Datta is an Assistant Professor in the disciplines of Chemistry and Biological Sciences at IIT Gandhinagar. His research interests include the investigation of groove-modified nucleobases on Y-family DNA polymerase activity, construction of metal nanowires based on biomolecular templates, and structure-function correlations of unorthodox DNA structures. Find out more about him at his website.