Forensic evidence will play a major part in the murder trial of paralympian Oscar Pistorius which begins tomorrow and will be broadcast live around the world.
The double-amputee athlete has always insisted he and model girlfriend Reeva Steenkamp had had a quiet night in together at his house, a closely guarded compound in Pretoria.
He claims he got up in the early hours to bring in a fan from the balcony. But when he went back into the bedroom again, in the pitch dark, he says he heard a noise.
Believed there was an intruder in the house, he says he grabbed a 9mm pistol that he kept under his bed that he kept for security purposes and ran down the passageway leading to the bathroom, without his prosthetic legs on.
There he fired four shots into the toilet door, which was closed. He insists it was only when he went back into the bedroom and realised his girlfriend was not in bed that it dawned on him it was her in the toilet.
Pictures inside the house show a trail of blood from the bathroom as the paralympian carried Ms Steenkamp downstairs after shouting for help, with flecks of blood on the wall, on the sofa downstairs and on the landing.
The case is likely to hinge on forensic evidence, with specialists for both the defence and prosecution trying to glean everything they can from the site of the shooting.
Ballistics expert JC de Klerk has told Sky News how every shot fired will have left a trail.
“The trajectory of bullets through the door will give an indication of where the firearm must have been held,” he said.
Forensic experts say every drop of blood can help show what happened, and whether Ms Steenkamp was sitting, standing or moving at the time she was shot.
Pistorius insists he was “deeply in love” with Ms Steenkamp, who he had been dating for just a few months.
When the world’s best-known paralympian appeared at Pretoria Magistrates’ Court during a bail application hearing, he said when he realised his mistake he did everything to save his lover, battering the toilet door with a cricket bat to get to her.
During the trial, science and forensics will help build a picture of what happened, and it will be down to a judge to decide whether the death of Ms Steenkamp was a tragic accident or murder.