Oscar Pistorius' girlfriend was standing in a toilet cubicle and facing the closed door when she was hit in the right hip by the first of four bullets fired by the double-amputee athlete, a police ballistics expert said.
Reeva Steenkamp then fell back on to a magazine holder in the cubicle and was struck in the right arm and head by the last two shots fired from the 9mm pistol through the door as she crossed her arms over her head to protect herself, Captain Christiaan Mangena said.
He testified that he believed the second bullet missed Ms Steenkamp and ricocheted off a wall inside the cubicle and broke into fragments, which caused bruising on her back.
Mr Mangena concluded, through his analysis of the shooting scene and wounds on Ms Steenkamp's body from post-mortem photos, that one bullet went through Ms Steenkamp's left hand before penetrating her skull as she held it over her head.
The policeman said he could not determine the order of the last two shots.
Pistorius, 27, is charged with premeditated murder over Ms Steenkamp's death on February 14 last year and faces 25 years to life in prison if convicted.
He says he shot Ms Steenkamp, 29, by mistake through a locked door in his bathroom because he thought she was a dangerous night-time intruder in his home.
Pistorius says Ms Steenkamp went to use the toilet during the night without him knowing, but prosecutors maintain he killed her after a loud argument that caused her to possibly flee and hide in the toilet area.
Mr Mangena said the bullet that struck Ms Steenkamp's skull broke into two fragments, one of which exited her head and struck the wall behind her. The first shot into the right hip broke Ms Steenkamp's hip bone, Mr Mangena said.
"I'm of the opinion that after this wound was inflicted, my lady, she dropped immediately," Mr Mangena said, addressing the judge in court under questioning from prosecutor Gerrie Nel. Ms Steenkamp slumped into a "seated or semi-seated position" on top of a magazine rack in the cubicle, where she was hit another two times.
"She ended up with her head on top of the toilet seat, and the lower part of her body on the rack, Mr Mangena said.
Pistorius fired from a distance of at least 60 centimetres (24in) and no further than a wall behind him, about three metres (10ft) away, Mr Mangena said.
He also described the impact of the type of bullets in Pistorius' gun, which were designed to cause maximum damage, he said.
"It hits the target, it opens up, it creates six talons, and these talons are sharp," Mr Mangena said. "It cuts through the organs of a human being."
He noted the Black Talon brand of ammunition was often used for self-defence because while it caused significant damage to a human target, it was less likely to penetrate the first target and hit other people.
Mr Mangena also said he conducted shooting tests to try to pinpoint the location from which the bullets were fired by Pistorius in the bathroom, based on where the cartridge cases were found. However, in his tests, he said, the cases fell at different angles. He also noted that the cartridge cases at the scene of Ms Steenkamp's shooting could have been "moved or kicked around" during the investigation.
He said Pistorius was probably on his stumps when he fired, supporting the athlete's statement that he was not wearing his prosthetic limbs when he opened fire.
Mr Nel also asked Mr Mangena to comment on a 2012 incident in which Pistorius allegedly fired his gun out of the sunroof of a moving car. The athlete faces a firearms charge in that case, as well as two other firearms charges.
Mr Mangena said firing a shot in such circumstances was dangerous.
The bullet leaves the barrel at around 280 metres (900 feet) a second, and will travel upward, then stop and fall to the ground under the force of gravity and wind deflection, he said.
"The bullet can still kill a person," Mr Mangena said.