Oscar Pistorius, the Blade Runner, has gone on trial in South Africa, accused of murdering his girlfriend, Reeva Steenkamp.
But with no eyewitnesses to Steenkamp’s death, the case will re forensic evidence. Can forensic evidence determine a murder trial?
Metro spoke with William Castro, professor of criminal justice at Becker College in Worcester, Massachusetts.
Metro: Which role does forensic evidence play in a murder trial where there are no eyewitnesses?
Castro: Even when there are witnesses, the problem with testimonial evidence is that human beings are flawed: we might remember incorrectly, we might be scared. With forensic evidence, every piece of evidence tells a story, and investigators have to take these individual stories and put them together. In the Oscar Pistorius trial, the testimonial evidence we have is that witnesses heard a woman scream behind a closed door. That’s why the bullets are so important.
Assuming that a thorough crime scene investigation was conducted at Oscar Pistorius’s home, investigators recovered the bullets, which can be matched to a specific weapon. If the victim’s body was still in place when they arrived, forensic scientists can also determine the location from where the weapon was fired, the height at which it travelled, its trajectory and how it entered the victim.
That plays a big role in Pistorius’s trial because he claims he didn’t have time to put on his prosthetic legs, thinking he had to fight off an intruder.
Yes, because if he was wearing his leg prostheses, the bullet traveled at one trajectory, and if he wasn’t, it travelled at a lower trajectory. The crucial part is that the crime scene mustn’t be tampered with. If that happens, there’s no going back.
So an ambulance crew shouldn’t touch a victim even if there’s a slight chance he or she might still be alive?
You have to value life over the investigation. That’s the difficulty. Ambulance medics don’t deliberately destroy a crime scene, but they lose hairs, they step on a footprint. If the victim is taken to the hospital, an investigator usually accompanies him or her because he might spot evidence on the body or clothes. The investigator should also attend the autopsy to document potential pre-existing illnesses, as that’s crucial evidence in a murder trial. The defense might claim that the victim died from an illness, not the violent act.