Colonel Schoombie van Rensburg, the first policeman to arrive at the athlete's home in an upmarket Pretoria estate, described the grisly sight that greeted him in the early hours of Feb. 14 last year.
During his testimony, photographs of Steenkamp's face and body were also shown accidentally to the court, upsetting Pistorius, who vomited into a bucket for the second time since the start of the trial, now in its second week.
Van Rensburg said that on his arrival at the home, he saw Steenkamp's body lying at the bottom of the staircase covered in towels and black bags. She had been declared dead by medics by the time he arrived.
Moments later, he found a "very emotional" Pistorius in the kitchen pacing up and down.
"I asked him what happened but he didn't answer me," Van Rensburg told the court. "He was in tears."
The colonel said a trail of blood led him up the stairs to Pistorius' bedroom and the bathroom where the Paralympic and Olympic star shot Steenkamp, whom he says he mistook for an intruder.
Pistorius' lower limbs were amputated as a baby but he overcame the disability to become the "fastest man on no legs", running on carbon-fibre "blades" to win gold medals at the Beijing and London Paralympics. He has pleaded 'not guilty' to murdering law graduate and model Steenkamp.
Prosecutors are trying to prove that the killing was premeditated. If found guilty of murder, Pistorius faces at least 25 years behind bars.
The court was shown photos of the blood-spattered bathroom floor on which lay a crumpled, blood-soaked towel and a cricket bat that Pistorius used to break down the bathroom door after shooting through it.
The photos showed empty bullet cartridges on the floor and the 9mm pistol with which Pistorious fired four shots. Steenkamp was hit three times: in the head, arm and hip.
Asked by state prosecutor Gerrie Nel what condition the firearm was in, van Rensburg said it was cocked, with the safety catch removed.
"It's ready to fire," he said, when shown a photo. "You just have to pull the trigger."
Van Rensburg, a police veteran of 29 years' service, was the commander of the nearby Boschkop police station at the time of the incident and had been on duty for 24 hours when he was called, he told the court.
He resigned from the police last December.
