By Adv Shivmani Yadav
In courtrooms around the world, the pursuit of justice depends on facts-clear, credible, and convincing. In criminal trials, perhaps no form of evidence carries more weight or promise than that grounded in science. Forensic evidence-whether DNA, fingerprints, blood patterns, digital traces, or ballistic reports-has transformed the legal landscape, offering courts tools once unimaginable a few decades ago. But this transformation comes with its own complications. Scientific evidence may appear ironclad on the surface, but it’s not immune to error, bias, or misuse. As forensic methods become more central to criminal trials, courts must continue to ask: is the science being applied responsibly, and does it truly serve justice?
The Emergence and Evolution of Forensic Science in Criminal Law
The use of scientific techniques to solve crimes is not a modern invention. Even in the 19th century, early forensic pioneers used rudimentary tools like fingerprinting or chemical tests for poisons. However, it was not until the latter half of the 20th century that forensic science truly began to take shape as a specialized, interdisciplinary field.
The watershed moment came with the introduction of DNA profiling in the 1980s. For the first time, the justice system had access to a tool that could identify or exclude individuals with astonishing precision. The courtroom, which had long relied on witness testimony, confessions, and circumstantial evidence, now had something closer to a biological signature.
Since then, the range of forensic disciplines has widened dramatically. Today, trials routinely involve evidence drawn from fields as diverse as ballistics, toxicology, computer forensics, forensic anthropology, and handwriting analysis. The science behind each may differ, but the goal is always the same: to uncover the truth about what happened, how, and who was responsible.
Yet, with greater reliance on forensic science comes a greater responsibility to ensure its reliability. Not all forensic methods are created equal. Some are built on decades of peer-reviewed research and strict protocols; others are more speculative, based on tradition rather than scientific consensus. The law must distinguish between the two, especially when a person’s liberty-or life-is on the line.
Admissibility: Who Decides What Science Belongs in Court?
Not all forensic evidence presented by the prosecution or defence makes it into the courtroom. Judges play a crucial role as gatekeepers, determining whether certain scientific evidence is admissible based on legal standards. In many jurisdictions, including the United States, this role is informed by the Daubert standard, which asks whether the method has been tested, whether it has been peer-reviewed, its known error rate, and whether it is generally accepted by the relevant scientific community.
This approach aims to prevent “junk science” from influencing verdicts. For instance, bite mark analysis-a once commonly accepted forensic method-has come under heavy scrutiny in recent years due to its subjective nature and a significant history of wrongful convictions linked to it. Similarly, microscopic hair analysis, once deemed reliable, has been largely discredited by scientific reviews and FBI admissions of past errors.
The legal system’s growing scepticism of such methods is a welcome development. It signals a shift toward a more cautious, evidence-based approach to forensic science. However, not all courts apply these standards uniformly, and some outdated or unreliable techniques still find their way into trials, often without challenge.
DNA Evidence: The Gold Standard, But Not Without Risks
Among all forensic tools, DNA evidence has the strongest reputation for accuracy and reliability. When collected, preserved, and analysed properly, a DNA match can powerfully confirm or refute a suspect’s presence at a crime scene. Countless cold cases have been solved-and wrongful convictions overturned-thanks to DNA.
However, it’s important not to be lulled into a false sense of certainty. The strength of DNA evidence depends heavily on the quality of the sample, the method of collection, and the context in which it is presented. Mistakes in the chain of custody, contamination, or laboratory errors can compromise results. Moreover, in some cases, the DNA recovered may belong to multiple individuals, making it harder to interpret conclusively.
There’s also the issue of secondary transfer-a phenomenon where a person’s DNA ends up on an object or surface they never directly touched, simply through contact with another individual or object. In such situations, presence does not necessarily equal participation in a crime. Defence attorneys increasingly point to these complexities to question whether DNA alone should determine guilt.
Forensic Experts: Guardians of Truth or Partisan Advocates?
Forensic science does not speak for itself-it speaks through experts. These individuals, trained in specific disciplines, are often called upon to interpret evidence and explain their findings to the jury. Ideally, they act as neutral presenters of facts. But the reality is often more complicated.
In most cases, forensic experts are hired by one side: either the prosecution or the defence. While many work with professionalism and integrity, the adversarial nature of the legal system introduces the risk of unconscious bias. Experts may feel pressure-whether spoken or not-to present findings in a way that supports the side that hired them.
Juries tend to place great trust in experts, especially those with impressive credentials or confident demeanours. But scientific testimony is often nuanced, filled with probability estimates, margins of error, and cautious conclusions. When presented without care, or when cross-examination is ineffective, jurors may take expert statements at face value without fully understanding their limitations.
To address this, some courts are experimenting with court-appointed neutral experts or panels of experts who represent a broader scientific consensus. These efforts aim to reduce bias and help juries focus on science rather than sides.
The Jury’s Challenge: Interpreting Science in the Courtroom
Perhaps one of the greatest challenges in forensic trials is not the science itself but how it’s received. Jurors are ordinary people, not scientists. They bring to the courtroom their own assumptions, beliefs, and, increasingly, exposure to crime dramas like CSI, Bones, or NCIS. These shows often portray forensic science as fast, infallible, and conclusive-an impression far removed from the reality of messy evidence, inconclusive results, and imperfect methods.
This so-called “CSI effect” has two consequences. On one hand, jurors may demand high-tech forensic proof even when it’s unnecessary or unavailable. On the other, they may place undue trust in any evidence labelled “scientific,” regardless of its actual reliability. Both scenarios can distort justice.
The responsibility falls on judges, lawyers, and experts to demystify forensic science. Complex terms should be translated into clear language. The strengths and limits of each method must be openly discussed. Jury instructions can also be tailored to clarify how scientific evidence should be weighed, not simply accepted.
The Road Ahead: Reform, Oversight, and a Healthy Dose of Scepticism
Forensic science has undeniable power-but that power must be wielded carefully. In recent years, several studies and investigations have exposed significant shortcomings in the forensic field. The 2009 report by the US National Academy of Sciences, for instance, raised alarm bells about the lack of standardization, oversight, and research underpinning many forensic techniques.
These concerns have sparked calls for reform. Independent forensic science commissions, standardized protocols, mandatory accreditation for labs, and continued scientific review are among the proposed solutions. There is also a growing emphasis on improving the education and training of forensic professionals-not only in their technical skills, but in ethical responsibilities and legal awareness.
The law must continue evolving to meet these challenges. Judges must stay informed. Lawyers must scrutinize evidence rigorously. And forensic scientists must hold themselves to the highest standards. Only then can forensic evidence truly serve as a force for justice, not a shortcut to conviction.
—Advocate Shivmani Yadav practices in Dwarka and Tis Hazari District and Session Courts, Delhi