Forensic Science On Trial: A Critical Analysis Of Dna Profiling, Polygraph Test, Finger Print Test, And Brain Mapping In The Indian Criminal Justice System

The increasing reliance on forensic science within the Indian criminal justice system marks a paradigmatic shift from testimonial to scientific evidence. While this development purports to bolster the accuracy and objectivity of criminal adjudication, it simultaneously raises profound concerns relating to the reliability, admissibility, and ethical contours of specific forensic techniques. This research critically examines four pivotal forensic tools, DNA profiling, polygraph testing, fingerprint analysis, and brain mapping, in the context of Indian law, jurisprudence, and evolving legislative frameworks, including the newly enacted criminal laws. Despite the scientific allure of DNA evidence and fingerprint analysis, their use remains fraught with procedural lacunae, infrastructural deficits, and an absence of regulatory oversight. Meanwhile, techniques such as polygraph and brain mapping, though frequently employed during investigations, have been declared inadmissible by the Supreme Court, primarily due to concerns surrounding voluntariness and the right against self-incrimination under Article 20(3) of the Constitution. The incorporation of Sections 349 and 93 in the Bharatiya Nagarik Suraksha Sanhita (BNSS), 2023, and Bharatiya Sakshya Adhiniyam (BSA), 2023, respectively, has expanded the scope of forensic collection and evidentiary admissibility; however, these provisions lack robust procedural safeguards and risk enabling coercive and intrusive investigatory practices. This research argues that forensic science, if uncritically embraced, risks supplanting constitutional protections with technocratic authoritarianism. It advocates for a rights-based, scientifically rigorous, and judicially restrained approach to forensic evidence, anchored in procedural due process, informed consent, and independent regulatory oversight, to prevent miscarriages of justice in the guise of scientific certainty.

Background & Context

The Indian criminal justice system is undergoing a transformative shift from reliance on testimonial evidence to scientific methods, raising critical questions about the intersection of forensic technology and constitutional rights. Historically, Indian criminal jurisprudence relied heavily on eyewitness testimony and confessions, often plagued by subjectivity and human error, before gradually incorporating scientific techniques like fingerprint analysis and DNA profiling in recent decades.

This critical legal review examines four major forensic techniques—DNA profiling, polygraph testing, fingerprint analysis, and brain mapping—within the framework of India's newly enacted criminal laws: the Bharatiya Nagarik Suraksha Sanhita (BNSS), 2023 and Bharatiya Sakshya Adhiniyam (BSA), 2023. These laws replace colonial-era statutes and expand forensic collection powers while introducing new evidentiary standards.

The research addresses a fundamental tension: forensic science, if uncritically embraced, risks supplanting constitutional protections with technocratic authoritarianism. This is particularly salient given India's constitutional safeguard against self-incrimination under Article 20(3) and the Supreme Court's landmark rulings on investigative techniques.

Research Design & Methodology

This is a doctrinal legal analysis examining forensic techniques through the lens of Indian constitutional law, statutory frameworks, and judicial precedent. The research synthesizes case law, legislative provisions, and legal scholarship to evaluate the admissibility, reliability, and ethical implications of forensic evidence in criminal proceedings.

The analysis focuses on several key legal sources:

• The Supreme Court's decision in Selvi v. State of Karnataka, which held that narco-analysis, brain-mapping, and polygraph tests violate the right against self-incrimination under Article 20(3) when forcibly administered
• Sections 349 of BNSS, 2023 and Section 93 of BSA, 2023, which have expanded the scope of forensic collection and evidentiary admissibility
• Constitutional provisions protecting personal liberty (Article 21) and the privilege against self-incrimination (Article 20(3))
• Established jurisprudence on physical versus testimonial evidence

The methodology involves comparative analysis of how different forensic techniques interact with constitutional protections, examining their scientific validity, procedural safeguards, and potential for abuse in investigative contexts.

Results & Key Findings

Polygraph testing remains categorically inadmissible in India despite its investigative use. The legal status of the polygraph test within the Indian evidentiary framework is one of categorical inadmissibility due to constitutional infirmities and questions surrounding its scientific validity; the BSA 2023 allows admissibility of electronic records and expert evidence but polygraph tests, lacking consistent scientific validation and universal standards, fail to meet the threshold of reliability contemplated by the new law and remain an investigative aid rather than an evidentiary tool.

The research identifies several critical distinctions:

• Polygraph and brain mapping, though frequently employed during investigations, have been declared inadmissible by the Supreme Court primarily due to concerns surrounding voluntariness and the right against self-incrimination under Article 20(3)
• The Supreme Court in Selvi case held that involuntary administration of such tests violates fundamental rights guaranteed under Article 20(3) and Article 21 of the Indian Constitution
• Even with consent, test results alone cannot be admitted as evidence since the subject lacks conscious control over responses; however, information discovered as a result of voluntarily administered tests can be admitted under Section 27 of the Evidence Act, 1872

The incorporation of Sections 349 and 93 in BNSS and BSA has expanded forensic collection scope, but these provisions lack robust procedural safeguards and risk enabling coercive and intrusive investigatory practices. Section 349 BNSS empowers a Magistrate to direct an accused to provide handwriting, signature, finger impressions, or voice samples, while Section 93 BSA allows courts to presume validity of electronic signatures on records that are five years old.

Discussion & Significance

This research makes an important contribution by critically examining India's forensic evidence framework at a pivotal moment of legal reform. The new criminal laws represent a paradigmatic expansion of state power to collect scientific evidence, yet they operate within constitutional constraints established by the Supreme Court in Selvi and related cases.

The analysis reveals a fundamental asymmetry: while DNA profiling and fingerprint analysis have gained acceptance as physical evidence not protected by Article 20(3), the Court held that polygraph test responses involve unique communicative value which ordinary physical evidence would lack. This distinction reflects the Court's concern that physiological responses to questioning constitute a form of testimonial compulsion.

The findings underscore persistent infrastructural and regulatory deficits in India's forensic ecosystem. Despite the scientific allure of DNA evidence and fingerprints, their evidentiary use remains compromised by procedural lacunae and absence of regulatory oversight. The research argues that without robust safeguards for chain of custody, informed consent protocols, and independent oversight, expanded forensic powers under the new laws may enable miscarriages of justice rather than prevent them.

Limitations & Considerations

As a doctrinal legal analysis, this research does not include empirical data on forensic technique accuracy, field reliability studies, or examiner performance metrics. The analysis is confined to India's legal framework and jurisprudence, limiting generalizability to other jurisdictions with different constitutional protections or evidentiary standards.

The research focuses primarily on the admissibility and constitutional dimensions of forensic techniques rather than their scientific validity or operational effectiveness in criminal investigations. While the paper critiques the lack of regulatory oversight, it does not propose detailed regulatory frameworks or implementation mechanisms. Additionally, the BNSS and BSA laws were only recently enacted (2023-2024), meaning their practical application and judicial interpretation remain evolving areas without extensive case law for analysis.

Practical Applications

For criminal defense practitioners and civil liberties advocates, this research provides a comprehensive framework for challenging coercive forensic testing and understanding the constitutional limits on investigative techniques. The analysis reinforces that polygraph and brain mapping results obtained without proper consent remain inadmissible, and even voluntary testing requires strict procedural safeguards including legal representation and informed understanding of rights.

For policymakers and law enforcement, the research highlights the urgent need for rights-based forensic protocols that balance investigative efficacy with constitutional protections. The authors advocate for independent regulatory oversight, mandatory chain-of-custody procedures, and standardized training for forensic examiners. Understanding these legal constraints is essential for prosecutors and investigators to ensure that forensic evidence withstands judicial scrutiny and that investigative methods do not violate defendants' fundamental rights under the Indian Constitution.