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 told a court.
He testified he believed the second bullet missed Ms Steenkamp and ricocheted off a wall inside the cubicle and broke into fragments, causing 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, denies 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 intruder in his home.
Mr Mangena said Ms Steenkamp slumped into a seated position on top of a magazine rack where she was hit another twice. The trial continues.