The evidentiary value of a toxicological finding is only as strong as the chain of custody that connects the biological sample analysed in the laboratory to the sample originally collected from the body of the victim, the accused, or the crime scene. Any unexplained gap in that chain—delay, defective sealing, mismatched documentation, or unauthorised handling—invites the inference that the sample analysed may not be the sample seized, undermining the entire evidentiary edifice built upon it. India's new criminal-law trilogy—the Bharatiya Nyaya Sanhita, 2023 (BNS), the Bharatiya Nagarik Suraksha Sanhita, 2023 (BNSS), and the Bharatiya Sakshya Adhiniyam, 2023 (BSA), all in force since 1 July 2024—introduces, for the first time, express statutory language addressing forensic investigation, custody chronology, and expert certification. This paper critically examines whether these reforms meaningfully strengthen the chain of custody specifically for toxicological evidence, drawing on the jurisprudence developed under the Narcotic Drugs and Psychotropic Substances Act, 1985, the Supreme Court's decisions in Mohan Lal v. State of Punjab, Tomaso Bruno v. State of Uttar Pradesh, and Anvar P.V. v. P.K. Basheer, and empirical evidence of delay and documentation failure in India's forensic science laboratories. It concludes that while the new laws formalise obligations that were previously matters of practice and precedent alone, they do not resolve the underlying infrastructural deficits that have historically produced custody breaks, and proposes a set of institutional and procedural reforms to close that gap.