Reeva Steenkamp then fell back onto a magazine holder in the cubicle and was struck in the right arm and head by the last two shots fired from the 9 mm pistol through the door as she crossed her arms over her head to protect herself, Capt Christiaan Mangena said.
He testified that he believed the second bullet shot missed Steenkamp and ricocheted off a wall inside the cubicle and broke into fragments, which caused bruising on her back.
The policeman said he couldn't determine the order of the last two shots.
Pistorius, 27, is charged with premeditated murder in Steenkamp's shooting death on February 14 last year and faces 25 years to life in prison if convicted. He says he shot Steenkamp, 29, by mistake through a locked door in his bathroom because he thought she was a dangerous nighttime intruder in his home.
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"I'm of the opinion that after this wound was inflicted, my lady, she dropped immediately," Mangena said, addressing the judge in court under questioning from prosecutor Gerrie Nel 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.
Pistorius fired from a distance of at least 60 centimeters and no further than a wall behind him, about 3 meters away, Mangena said. Mangena 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," Mangena said. "It cuts through the organs of a human being."
He noted the Black Talon brand of ammunition was often used for self-defense because while it caused significant damage to a human target, it was less likely to penetrate the first target and hit other people.