A crucial question often asked in investigations is whether a human action, condition or event is physically possible or capable of causing an observed effect. Some events, however, cannot be replicated in an experiment due to the overriding safety of human subjects. This is where forensic simulations can provide vital assistance.
Forensic simulations pose unique challenges as they require not only the perspective of the incident or crime, and the investigative requirements, but also an understanding of the model to adopt and construct in order to simulate the circumstances of an incident, and to record and interpret its observed effects to obtain reliable scientific findings.
Case study 1: Fall from a height
One of the better-known cases where forensic simulation proved useful was the PP v Chee Cheong Hin Constance case. It was crucial for the Court to determine how a 4-year old girl whom Constance was carrying fell to her death. Did she accidentally fall over the parapet wall of the HDB block or was she deliberately thrown down by Constance?
On 7 October 2004 at about 4.44 a.m., Neo Eng Tong and his wife awoke from their sleep to find their 4-year old daughter, Sindee missing. Rushing out of their flat and running downstairs to look for her, the couple heard cries and witnessed their only daughter fall from a storey above and crash through the walkway shelter onto the ground at the foot of the block. Constance Chee, Neo’s lover was charged with kidnapping Sindee and causing her fatal fall. Experiments were conducted by our forensic experts to determine the distances from the building a 25-kg simulated load would fall, based on the pushing effort of a woman similar in weight and height to Constance. Interpretation using physics of these distances was instrumental in assisting the Court in its judgment.
Forensic simulations are not only widely employed in criminal cases such as fall from heights, traffic collisions and controversial suicides, but also play a vital role in civil cases. Our experts have conducted forensic simulations for civil matters involving workplace safety incidents, fires and explosions.
Case study 2: Damaged pneumatic tubings in a pharmaceutical manufacturing plant
Pneumatic tubes connected to a device in a pharmaceutical manufacturing plant were found to be fractured for no apparent reason. The client wanted to find out whether the tubings had been deliberately damaged as a sabotage attempt, or had failed mechanically without human intervention during operation. Simulation experiments were performed on control samples of similar tubings, and their damaged ends compared microscopically. Findings ruled out human intervention; the features on the ends of the questioned tubings were consistent with material failure due to wear and tear.
No two forensic scenes are similar, and some level of customisation is required for each simulation. Forensic simulations are not without pitfalls as the simulation findings are only as good as the inputs and processes that have been injected, i.e., garbage input results in garbage output. More importantly, an event that is physically possible does not mean it occurred in reality; other evidence needs to be evaluated and interpreted holistically with the simulation findings. Such cases therefore often require a team of multi-disciplinary and experienced forensic scientists, with a good grasp of the context of the case, to appropriately and sufficiently scope, design, and carry out the forensic simulations, interpret the findings and provide reliable conclusions and expert opinions on the case.