Impact of Forensic Evidence in the Tonu Murder Case under Law

The murder of Sohagi Jahan Tonu on 20 March 2016 remains one of the most unresolved and legally significant criminal cases in Bangladesh.

The case not only reflects investigative delays but also demonstrates how limitations and mismanagement of forensic evidence can directly affect the administration of justice under Bangladeshi law. Over the past decade, the inability to reach conclusive forensic determination has significantly weakened the legal process, raising serious concerns regarding evidentiary standards, procedural compliance, and institutional accountability.

Forensic evidence plays a central role in criminal trials in Bangladesh, particularly in cases involving homicide. Under the Bangladesh Penal Code, 1860, offences such as culpable homicide (Section 299) and murder (Section 300) require clear establishment of the cause and manner of death. This determination is primarily dependent on medico-legal evidence obtained through post-mortem examinations. In the Tonu case, however, both the initial and subsequent autopsy reports failed to definitively establish the cause of death. This absence of clarity has created a fundamental evidentiary gap, making it difficult for investigators to determine whether the death resulted from homicide, sexual violence, or other causes.

The first post-mortem examination reportedly found no evidence of rape and did not conclusively determine the cause of death. Due to public concern and legal pressure, a second autopsy was conducted following a court order. However, the second examination also failed to provide a clear forensic conclusion. Under the Code of Criminal Procedure, 1898, post-mortem reports are considered critical documentary evidence, and inconsistencies or inconclusive findings significantly reduce their probative value. Courts in Bangladesh generally rely heavily on medical evidence to corroborate witness testimony and circumstantial evidence. In its absence, the prosecution’s burden to prove guilt beyond reasonable doubt becomes substantially more difficult.

The role of forensic evidence is further governed by the Evidence Act, 1872, which allows expert opinions, including those of medical professionals and forensic analysts, to be admitted in court. However, such opinions must be clear, consistent, and scientifically reliable. In the Tonu case, the conflicting and inconclusive nature of the autopsy reports undermines their admissibility and weight as expert evidence. This situation creates a legal disadvantage for the prosecution, as defense counsel may easily challenge the credibility and reliability of such findings.

Another significant aspect of the case is the delayed application of DNA testing. The Police Bureau of Investigation (PBI), which took over the investigation in 2020, has recently sought to conduct DNA analysis by comparing biological samples collected from the victim’s clothing with those of certain individuals. While DNA evidence is widely recognized as one of the most reliable forms of forensic identification, its effectiveness is highly dependent on timely collection, proper preservation, and maintenance of chain of custody.

Under Bangladeshi evidentiary principles, any break in the chain of custody can render forensic evidence questionable or inadmissible. Given that nearly a decade has passed since the incident, concerns naturally arise regarding the integrity of the biological samples. Degradation, contamination, or improper storage could significantly affect the reliability of DNA results. If such issues are established during trial, the defense may argue that the evidence lacks credibility, thereby weakening the prosecution’s case.

The Tonu case also raises serious concerns about potential interference in the forensic process. Reports of threats directed at the forensic examiner and the victim’s family suggest the possibility of obstruction of justice. Under general principles of criminal law, any attempt to influence forensic findings or intimidate witnesses constitutes a serious offence and undermines the fairness of the judicial process. Such interference not only affects the quality of forensic evidence but also raises broader questions about the independence of medico-legal investigations in Bangladesh.

Additionally, the location of the crime within a military cantonment introduces jurisdictional and procedural complexities. While civilian law enforcement agencies retain authority over criminal investigations, the involvement of a restricted or sensitive area may limit access to evidence and delay forensic procedures. In the absence of clear coordination between relevant authorities, crucial forensic opportunities may be lost, further weakening the evidentiary foundation of the case.

The repeated transfer of the investigation among multiple agencies, including local police, Detective Branch, CID, and the PBI, has likely contributed to inconsistencies in forensic handling. Each agency may have followed different procedures or priorities, resulting in fragmented evidence collection and analysis. Under criminal law, consistency and continuity in investigation are essential to ensure that forensic evidence remains coherent and legally sustainable.

Although the Tonu murder case was significantly delayed in its effective investigation, there are many instances where justice has still been ensured despite proceedings beginning at a later stage. Therefore, it is reasonable to remain hopeful that the Tonu murder case may also ultimately result in proper judicial determination and accountability.

In the Conclusion this is an old case, there is still a ray of hope now that the proceedings have finally begun in an effective manner. Through the renewed investigation, several suspects have reportedly been brought under the scrutiny of law enforcement, which may make the pursuit of justice more achievable. However, if these investigative steps had been taken from the very beginning, forensic evidence could have been far more effective and reliable in establishing the truth. Delays in criminal investigations often weakens the evidentiary value of forensic materials, as physical evidence may deteriorate, disappear, or become contaminated over time. Nevertheless, it is encouraging that even after ten years, the Tonu murder case has once again been brought within the active framework of the law, reaffirming the importance of forensic evidence in ensuring accountability and justice in criminal trials.

Rokeiya Tahia: LL. B LL.M, Bangladesh University of Professionals.