forensic evidence

Forensic evidence is an international legal concept denoting physical traces, objects or information collected at a crime scene or in connection with a crime and subsequently subjected to scientific analysis for use as evidence in a criminal case. The concept is not anchored in the legislation of any one country, but constitutes a fundamental category within international criminal law and criminalistics.

Forensic evidence covers a broad spectrum of evidentiary material: DNA profiles, fingerprints, ballistic examinations, toxicological analyses, bloodstain analysis, digital traces and forensic autopsy findings. What they have in common is that they rest on recognised scientific methods and can be presented in court as professionally substantiated evidence.

In cases such as the Koh Tao murders, forensic evidence forms the pivot of the debate over the credibility of the investigation — including whether DNA traces were correctly collected and analysed, and whether the chain of custody can be regarded as unbroken. In the Kathleen Peterson case, the forensic findings were decisive for the dispute over whether the death was caused by a fall or by an act of violence, as bloodstain patterns and the extent of the injuries were interpreted in widely differing ways by the prosecution's and the defence's expert witnesses. In cases such as the Mørkeland killing, forensic evidence in the form of digital and technical traces can help uncover the course of events, even where a rational motive is apparently absent.

A central principle is that forensic evidence does not in itself establish guilt. Rather, it establishes — with a certain degree of scientific certainty — facts about the event: who was present, what happened, and when. The weight of the evidence depends on the recognised standard of the analytical methods, the competence of the expert, and the integrity of the chain of custody from the crime scene to the courtroom.

In international criminal cases and cross-border investigations, forensic evidence is particularly significant because it provides an objective basis that can in principle be assessed independently of jurisdiction and legal system — although the standards for collecting, storing and presenting such material vary considerably from country to country.