Pretoria: He threaded steel rods through bullet holes, and tracked likely trajectory paths with lasers.
He immersed himself in Oscar Pistorius’ bathroom crime scene, and studied the three gunshot wounds to Reeva Steenkamp’s body.
Captain Chris Mangena is expected to tell the court on Wednesday why he concluded that the double-amputee was not wearing his prosthetic legs the night he shot and killed his model girlfriend.
His ballistics report is a key plank of the state's case for murder, and was enough to change the case theory presented by the prosecution.
Police had originally alleged Pistorius was wearing his prostheses when he fired four shots from his 9mm pistol into the toilet cubicle door, but Mangena's report changed that.
On Tuesday afternoon, the police officer of 20 years – 19 of which have been spent in the ballistics field – began his evidence, taking Pistorius’ murder trial through the intricacies of his crucial case.
Captain Mangena told the Pretoria High Court he was called into investigate the shooting on March 7 last year, three weeks after the alleged crime, and he began by examining the toilet cubicle door.
He reassembled it, putting back the missing panels broken out as Pistorius tried to reach his girlfriend in the wake of the shooting, and marking the four clear bullet holes. The next day he took it back to the crime scene.
“The door was replaced in exactly the same way it was before it was moved,” he said, explaining he used identical screws and fittings to those removed.
He began by measuring the distance from the floor to the holes, telling the court they ranged from 93.5cm to 104.3cm from the tiles.
The ballistics expert requested photographs of the crime scene as it was found that morning.
Only one bullet had lodged into the wall behind the door, after ricocheting off another wall.
Mangena told the court that the bullet trajectory was between five and six degrees below horizontal.
The other three bullets had gone through the toilet door and not struck a wall, meaning they had lodged in Ms Steenkamp. The court has previously heard she was struck in the hip, shoulder and head.
In order to examine the likely trajectories of those shots, Mangena said he requested autopsy photos of Ms Steenkamp’s injuries so he could try and work out the point where the bullets had originated.
“My lady, for me to reconstruct the scene, I had to see the condition of the deceased,” he said.
He also examined bruising to Ms Steenkamp’s chest and back, likely from shrapnel wounds, and also assessed the version of events given by Pistorius at his bail application to use it as a “benchmark.”
As a result of Pistorius’ claim that he was on his stumps when the shots were fired, Mangena requested measurements be taken of the accused with and without his prosthetics: the athlete stands 184cm with his prosthetic legs on, and 155cm without.
His shoulder height with them on is 156cm, and 123cm just on his stumps.
As Mangena discussed Ms Steenkamp's wounds, explaining the entry and exit points, the model’s mother June was comforted by an ANC Women’s League friend.
Pistorius put his fingers in his ears, bending partially over a notepad on his knee.
Earlier, lawyers for the Olympian and Paralympics gold medallist painstakingly tried to show how police contaminated the crime scene and carelessly dealt with evidence.
Barrister Barry Roux, for Pistorius, presented a series of photographs showing the alleged murder weapon and a cricket bat used to break down the toilet door after the shooting, among a variety of exhibits in different positions.
He said there appeared to be another photographer at the scene – however, crime scene photographer Bennie van Staden rejected any claims he moved things prior to photographs being taken.
Mr Roux was also criticised for badgering the witness, earning a sharp rebuke from trial judge Thokozile Masipa.
The case continues on Wednesday.