Though the accuracy of DNA evidence may be increasing with the advancement of science with every passing day, thereby making it more and more reliable, scientists have not yet reached a juncture where it may be said to be infallible. 

• Thus, it cannot be said that the absence of DNA evidence would lead to an adverse inference against a party, especially in the presence of other cogent and reliable evidence on record in favour of such a party.

About DNA

DNA is deoxyribonucleic acid, and it is genetic material present in the nuclei of cells in living organisms. 

• Presence: An average human body is composed of about 100 trillion cells. DNA is present in the nucleus of a cell as a double helix, supercoiled to form chromosomes along with intercalated proteins. 
• Genetic Structure: All information about internal organisation, physical characteristics, and physiological functions of the body is encoded in DNA molecules in a language (sequence) of alphabets of four nucleotides or bases: Adenine (A), Guanine (G), Thymine (T), and Cytosine (C), along with the sugar phosphate backbone.
• Chromosomes: Twenty-three pairs of chromosomes are present in each nucleated cell, and an individual inherits 23 chromosomes from the mother and 23 from the father transmitted through the ova and sperm, respectively. 
  • Chromosomes are threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell. 
• Source of Biological Material: Since the same DNA sequence is present in every cell of the body (apart from mature red blood cells) therefore, DNA can be sourced from any biological material. 
  • This includes saliva, semen, vaginal fluids, blood, body tissues, teeth, hair, and bones. 
  • DNA may be left behind on objects during physical contact, which is commonly referred to as touch DNA or trace DNA. 
  • The quantity of DNA contained in biological material varies. 
    • Blood and saliva are richer sources of DNA as compared to teeth and hair roots, which are DNA deficient. 
    • Touch DNA contains very low amounts of DNA and is not an ideal source for DNA profiling. 
  • The method for the collection, packaging, storage, and transportation of a DNA sample differs based on the source of the biological material and the conditions in which it is found. 

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Reliability of DNA in Criminology

DNA analysis is based on probability and, in that sense, cannot be considered conclusive evidence. DNA in all human beings is 99.9% identical. In forensic DNA profiling, a few locations in the remaining 0.1% of DNA are chosen to create a person’s DNA profile. 

• Loci: Theses are the specific locations at which the DNA. These loci have repetitive sequences of DNA called Short Tandem Repeats, or STRs. While every individual has the same sequence, or STR, on a locus, the number of times that it repeats itself may vary across individuals. 
• Alleles: The variation in the number of repetitions is referred to as alleles. 
  • At a given locus, an individual has two alleles, one inherited from the father and the other from the mother. STRs present on the Y chromosome are used in sexual assault cases or to determine paternal lineage.
• Need to Ensure: One way to ensure at least the right samples are tested is to videograph the entire process, following in Tamil Nadu due to a directive by Justice P.N. Prakash. He said that convictions cannot be made only on the strength of a DNA analysis, without other corroborating evidence.
• In Pattu Rajan v. State of T.N. 2019, judges considered the value to be attached to a DNA report: “Like all other opinion evidence, the probative value accorded to DNA evidence also varies from case to case, depending on facts and circumstances and the weight accorded to other evidence on record, whether contrary or corroborative. 

About DNA Profiling

DNA profiling is the process where a specific DNA pattern, called a profile, is obtained from a person or sample of bodily tissue. 

• Refers: DNA profiling, also known as DNA fingerprinting, is a  scientific technique employed to identify individuals based on their unique genetic makeup.
• Background: The genesis of DNA profiling can be traced back to the mid-1980s, British geneticist Alec Jeffreys discovered that certain regions of DNA contained patterns that were unique to each individual. 
  • His breakthrough led to the first-ever application of DNA profiling in a criminal case in 1986, marking the dawn of a new era in forensic science.
• Focus On: It involves analysing specific areas of the human genome, where variations between individuals are likely to exist. 
  • This enables an unparalleled level of discrimination, being able to distinguish between two individuals except for identical twins who share the same genetic blueprint.

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DNA Profiling Techniques

Various techniques have been developed over the years to unlock the power of DNA for identification and analysis:

• Restriction Fragment Length Polymorphism (RFLP): RFLP was the first method developed for DNA profiling. This process involves extracting DNA, cutting it into fragments using restriction enzymes, and then separating these fragments according to size using a process called electrophoresis.
• Polymerase Chain Reaction (PCR): PCR is a technique used to amplify specific regions of DNA, making it easier to analyse. It has proved indispensable in cases where only a small amount of DNA is available.
• Short Tandem Repeats (STR) Analysis: STR analysis focuses on specific regions of DNA that contain short sequence repetitions. The number of these repeats varies between individuals, making it a useful tool for profiling.
• Single Nucleotide Polymorphism (SNP) Analysis: SNPs are variations at a single base pair in the DNA sequence. With millions of SNPs spread across the human genome, their analysis can provide a detailed DNA profile.

Applications of DNA Profiling

Following are the various applications of DNA Profiling:

• Criminal Investigation and Forensics: DNA profiling plays a critical role in the field of forensic science. It is employed to link suspects to crime scenes.
• Paternity Testing and Genealogy: DNA profiling offers a reliable method for establishing biological relationships in paternity disputes and in exploring ancestral lines in genealogical research.
• Personalised Medicine and Genetics: The use of DNA profiling in medicine is increasing. It helps in understanding a patient’s predisposition to certain diseases and providing treatments according to their genetic makeup, leading to more effective and personalised healthcare.
• Wildlife and Conservation Genetics: In wildlife and conservation, DNA profiling helps track animal migration, monitor genetic diversity, and manage breeding of endangered species.

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Ethical, Legal, and Social Implications

Human DNA profiling is a powerful tool with vast applications in various fields. As it continues to evolve, it holds the promise of breakthroughs that could transform our understanding of human genetics and redefine personalised medicine. The integration of AI and machine learning techniques may revolutionise this field, making profiling faster, cheaper, and more precise.

• Privacy Concerns and Consent: The proliferation of DNA profiling has raised significant privacy and consent issues. The potential misuse of genetic data can lead to discrimination and breaches of privacy.
• Potential for Misuse: Inappropriate use of DNA profiling could result in genetic determinism and stigmatisation. It could also be exploited for purposes of surveillance and control.
• Ethical Dilemmas: The growth of direct-to-consumer genetic testing has triggered debates around the ethical implications of individuals having access to their genetic information, with concerns about psychological impact and potential for misunderstanding results.

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