Screening Science and Technology in the Courtroom: Judicial Practices and Procedures

When a forensic expert walks into a courtroom and claims that DNA evidence, a polygraph result, or a digital footprint proves an accused’s guilt, judges face a pressing challenge: how do they assess whether that science is actually reliable? Courts are not laboratories, and judges are not scientists. Yet every day, legal outcomes hinge on scientific and technological evidence that can be highly complex, contested, or simply wrong. The judiciary has therefore developed structured practices and procedures to screen such evidence before it ever influences a verdict – separating genuine science from what is often called “junk science.”

Why screening scientific evidence matters 🔗

Science evolves rapidly, and courts must keep pace. New forensic techniques, digital surveillance tools, biometric identification methods, and neuroscientific tests constantly find their way into criminal trials. Without a systematic gatekeeping process, unreliable or speculative scientific claims could sway juries and judges, leading to wrongful convictions or acquittals. The integrity of adjudication depends on ensuring that only sufficiently reliable and relevant scientific evidence is admitted. This is not a procedural formality – it is a constitutional and evidentiary necessity.

In India, the admissibility of expert scientific evidence is primarily governed by Section 45 of the Indian Evidence Act, 1872, which allows courts to consider the opinions of persons “specially skilled” in science, art, foreign law, handwriting, or finger impressions. With the enactment of the Bharatiya Sakshya Adhiniyam (BSA) in 2024, this framework has been modernised. Section 39 of the BSA retains the core principle but crucially adds “any other field” as a category for expert opinion, significantly widening judicial access to expert knowledge in emerging domains like cybercrime and digital forensics.

The foundational standards: Frye and Daubert 🔗

To understand how courts screen scientific evidence, two landmark standards from American jurisprudence are essential reference points – and they carry significant influence on Indian judicial thinking as well, particularly as referenced in the Supreme Court’s own decisions.

The Frye standard: general acceptance 🔗

The Frye standard, originating from Frye v. United States (1923), holds that expert scientific testimony is admissible only when the technique on which it is based has been “generally accepted” as reliable within the relevant scientific community. Under this test, the scientific community itself acts as the gatekeeper. If a method or theory has gained widespread recognition among specialists, the court treats it as reliable without independently scrutinising the methodology. This approach is conservative by design – it keeps experimental or fringe science out of the courtroom until the broader scientific community has vetted it.

The limitation of the Frye test is equally apparent: it can exclude credible new science simply because it has not yet achieved widespread adoption. A technique may be methodologically sound and empirically validated, yet be too recent to have gained general acceptance. In such cases, Frye would keep valuable evidence out of court altogether.

The Daubert standard: the judge as gatekeeper 🔗

The more flexible and widely influential standard emerged from the U.S. Supreme Court’s decision in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993). The Court held that the trial judge must act as a “gatekeeper,” independently evaluating whether an expert’s reasoning and methodology are both scientifically valid and relevant to the facts of the case. General acceptance is just one factor among several – not a prerequisite.

The Daubert framework lists the following non-exclusive criteria for assessing scientific reliability:

• Testability: Can the theory or technique be – or has it been – tested?
• Peer review and publication: Has the methodology been subjected to scrutiny by the broader scientific community through peer-reviewed publications?
• Known or potential error rate: What is the margin of error of the technique, and are there established standards to control it?
• Maintenance of standards: Are there professional standards governing the technique’s application?
• General acceptance: Is the method accepted within the relevant scientific community?

The Daubert standard was further expanded in Kumho Tire Co. v. Carmichael (1999), where the U.S. Supreme Court clarified that the gatekeeping role applies not only to purely scientific testimony but also to expert testimony based on “technical or other specialised knowledge.” This is particularly relevant in legal contexts involving digital forensics, engineering analysis, or medical diagnosis. The National Institute of Justice notes that under this framework, pertinent evidence based on scientifically valid principles will generally satisfy the reliability threshold, while guesswork and speculation will not.

How Indian courts screen scientific evidence 🔗

India does not have a codified Daubert-style hearing mechanism. However, Indian courts have developed an analogous judicial screening approach through statutory interpretation and landmark judgments. The process is guided by two threshold conditions under Section 45 (now mirrored in Section 39 of the BSA): first, the subject matter must be beyond the ordinary understanding of the court, making expert input necessary; second, the person offering the opinion must genuinely be an expert in that field. Courts do not automatically defer to anyone who claims expertise – qualifications, training, methodology, and experience are all scrutinised.

Importantly, expert opinion under Indian law is treated as advisory, not conclusive. As the Supreme Court clarified in State of Karnataka v. J. Jayalalitha, an expert does not decide facts – they furnish the court with the scientific criteria needed to evaluate conclusions. The court remains the ultimate decision-maker. A conviction cannot rest solely on expert opinion; it must be corroborated by other evidence. As observed in Jalapathi Reddy v. Baddam Pratapa Reddy (2019) 14 SCC 220, courts must exercise caution against placing undue reliance on expert evidence in isolation.

The problem of “junk science” 🔗

The term “junk science” refers to scientific testimony that appears credible on the surface but lacks genuine methodological rigour – either because the underlying theory is not falsifiable, the error rates are unacceptably high, or the technique has not been validated by the scientific community. Without proper judicial screening, junk science can masquerade as reliable evidence and mislead courts. The concern is not hypothetical. In India, debates have emerged around techniques like narcoanalysis, polygraph tests, and Brain Electrical Activation Profile (BEAP) testing, all of which have been marketed as scientific aids to criminal investigation, yet face serious questions about their scientific validity.

Selvi v. State of Karnataka: India’s landmark on scientific evidence screening 🔗

The most significant Indian judgment on judicial screening of scientific and technological evidence is Selvi & Ors. v. State of Karnataka (AIR 2010 SC 1974). A Constitutional Bench of the Supreme Court examined whether the involuntary administration of narcoanalysis, polygraph (lie detector) tests, and BEAP (brain mapping) tests in criminal investigations was constitutionally valid. The Court’s analysis went far beyond constitutional rights – it engaged deeply with the question of whether these scientific techniques were reliable enough to produce admissible evidence.

The Supreme Court in Selvi itself referenced the Frye and Daubert standards while evaluating these techniques. It found that narcoanalysis, for instance, could produce false and irrelevant information, that polygraph results were vulnerable to countermeasures by the subject, and that BEAP tests could be defeated if the subject had prior exposure to the relevant stimuli. On reliability grounds alone, the results of these tests – when obtained without consent – were deemed inadmissible. The Court ruled that involuntary administration of these techniques violates both Article 20(3) (right against self-incrimination) and Article 21 (right to life and personal liberty) of the Constitution. Even where consent is given voluntarily, results from these tests are treated as statements made to police under Section 27 of the Evidence Act – not as confessions, and not as standalone proof.

The judgment in Selvi effectively applied a reliability-and-consent-based screen to emerging forensic technologies. It demonstrated that Indian courts are capable of and willing to evaluate the scientific basis of novel evidentiary techniques, not merely their procedural propriety.

DNA and digital evidence: the expanding frontier 🔗

Where techniques like narcoanalysis struggled to pass judicial scrutiny, DNA evidence has been progressively accepted as reliable by Indian courts. The case of Kunhiraman v. Manoj established that DNA expert reports are admissible under Section 45 of the Indian Evidence Act, provided they are produced by qualified experts whose testimony can withstand judicial scrutiny. Courts have since mandated DNA testing in serious criminal cases such as rape, and forensic guidelines now emphasise accredited laboratories, unbroken chain of custody, and qualified expert testimony as prerequisites for admissibility.

On the digital side, Section 45A of the Indian Evidence Act (now reflected in Section 39(2) of the BSA) was inserted to specifically address electronic evidence. It allows the opinion of the Examiner of Electronic Evidence – a designated expert under Section 79A of the Information Technology Act, 2000 – to be treated as expert testimony. This provision equips courts to handle cybercrime cases, electronic records, and digital forensics with the same structured evidentiary framework applied to traditional scientific evidence.

Key principles guiding judicial screening 🔗

Drawing from both Indian law and comparative jurisprudence, the judicial screening of science and technology in the courtroom is governed by the following core principles:

• Relevance: The scientific evidence must be directly relevant to a fact in issue. It should help the court determine something material to the case, not introduce tangential technical detail.
• Reliability of methodology: The technique or theory underlying the evidence must be based on a sound scientific method – one that has been tested, subjected to peer review, and validated with acceptable error rates.
• General acceptance: While not the sole criterion under Indian law, acceptance of the methodology within the relevant scientific community carries significant weight.
• Qualified expertise: The person offering the opinion must have demonstrated, specialised knowledge in the relevant field. Bare assertions without supporting data, methodology, or credentials are treated with scepticism.
• Corroboration: Scientific or expert evidence in India does not stand alone. Courts require it to be consistent with – and supported by – independent direct or circumstantial evidence.

As the Supreme Court observed in State of H.P. v. Jai Lal and reiterated in numerous subsequent decisions, an expert must not merely state a conclusion – they must furnish the reasoning, data, and scientific basis that allow the court to independently evaluate that conclusion. Bare expert opinion, without supporting data or methodology, is insufficient even if technically admissible under Section 45 of the Indian Evidence Act.

Challenges and the road ahead 🔗

India’s approach to screening scientific evidence remains largely judge-dependent and case-specific. Unlike the structured pre-trial Daubert hearings in U.S. federal courts, Indian courts typically evaluate the reliability and relevance of scientific evidence during the trial itself, often in the absence of a dedicated mechanism. Legal scholars and researchers have consistently noted the need for India to formulate clearer, codified standards – similar in spirit to the Daubert criteria – for assessing the admissibility of scientific and technological evidence.

The enactment of the Bharatiya Sakshya Adhiniyam in 2024 represents a step in the right direction. By expanding the scope of expert opinion to include “any other field” and by separately addressing electronic evidence experts, Parliament has acknowledged that the evidentiary landscape of the 21st century extends well beyond handwriting and fingerprints. Yet the absence of explicit guidelines on methodology, error rates, and peer review – the very criteria that make Daubert so effective – means that Indian courts continue to rely heavily on judicial discretion when screening novel scientific evidence.

As forensic technology evolves – from AI-based facial recognition to algorithmic risk assessment tools – the pressure on judges to make informed, principled decisions about scientific evidence will only increase. The goal is not to turn courts into scientific bodies, but to ensure that every piece of scientific testimony that shapes a verdict has crossed a minimum threshold of reliability and relevance.

What do you think? Given that Indian courts largely rely on judicial discretion when evaluating scientific evidence, should India adopt a formal, codified screening mechanism similar to the Daubert standard – and if so, how should judges with limited scientific backgrounds be equipped to apply it? As emerging technologies like AI-based forensics and neuroimaging enter Indian courtrooms, do you think the current framework under the Bharatiya Sakshya Adhiniyam is sufficient to prevent “junk science” from influencing verdicts?

References

1. https://indiankanoon.org/doc/1025384/
2. https://www.law.cornell.edu/wex/frye_standard
3. https://www.expertinstitute.com/resources/insights/daubert-vs-frye-navigating-the-standards-of-admissibility-for-expert-testimony/
4. https://nij.ojp.gov/nij-hosted-online-training-courses/law-101-legal-guide-forensic-expert/pretrial/pretrial-rules-evidence/daubert-and-kumho-decisions
5. https://www.lawctopus.com/clatalogue/clat-pg/expert-opinion-under-indian-evidence-act/
6. https://indiankanoon.org/doc/338008/
7. https://bhattandjoshiassociates.com/transforming-criminal-justice-supreme-courts-landmark-dna-evidence-guidelines-in-kattavellai-vs-state-of-tamil-nadu/
8. https://www.apnilaw.com/legal-articles/acts/section-45-of-the-indian-evidence-act-vs-section-39-of-the-bharatiya-sakshya-adhiniyam-expert-evidence-and-opinions-of-experts-explained/
9. https://thelawbrigade.com/wp-content/uploads/2019/06/Sambeeta-Dabral.pdf