Their job: to search for clues to the truth behind the Blade Runner's killing of his supermodel girlfriend and lawyer, Reeva Steenkamp.

With specialised equipment they will use the patterns of the many splatters of blood in Pistorius's bedroom, and in other parts of his house, to piece together what happened at the moment of the killing and immediately afterwards.

A policeman close to the case said Steenkamp, 29, had been found in her nightwear when the police arrived at the scene. This could not be officially confirmed.

Brigadier Denise Beukes, of Gauteng police headquarters, refused to comment.

The news that Pistorius, 26, had killed his girlfriend reverberated across the world yesterday.

First reports said that he had mistaken her for an intruder.

But during the course of yesterday a much more complex picture emerged as veteran police officers - including members of the Investigative Psychology Unit, which investigates serial killings and psychologically motived murders - examined Pistorius's version of events.

In his statement Pistorius said that he was woken by a noise at about 3.45am. He grabbed his 9mm pistol and shouted a warning before firing four shots at "the intruder".

But the bullets found their mark in Steenkamp.

Pistorius shot her twice in the head, once in the arm and once in a leg.

The officers' questions come as police confirmed that there were previous domestic incidents and that the complex's security guards had attended to a disturbance complaint the night of the killing.

Beukes, of Gauteng police headquarters , said that there had been previous incidents "of a domestic nature" at Pistorius's home.

"During our investigation we received information that the complex's security management attended to a commotion earlier in the evening.

"Detectives are taking statements from the security management, as well as from neighbours who reported the commotion and the shooting," she said.

Beukes said four shots had been heard by Pistorius's neighbours.

"There is a possibility that more shots were fired ... our ballistic investigators are searching the scene for more bullets.

"The only two people in the house were the deceased and the suspect, who has now been charged with murder."

Beukes said Pistorius's licensed 9mm pistol had been sent for ballistic testing.

"The investigation is at an early stage. Our crime-scene specialists will return today to gather additional vital evidence."

According to police sources, it was a neighbour who called the police after hearing a commotion, not Pistorius. Beukes confirmed this.

Pistorius was yesterday questioned several times, first at his Pretoria home then at the Mamelodi Day Hospital, where his blood and urine were tested for drugs.

There was more interrogation at Boschkop police station, where he spent last night in one of the two communal cells.

A policeman described Pistorius's demeanour as "incredibly calm and collected" though he had wept at first during questioning.

"One moment he was weeping like a baby, the next he was cool, calm and collected. It was like that throughout the day ... at times it looked like he was not fazed by what had happened."

Family members who had been allowed to bring Pistorius a change of clothing while he underwent medical tests, and at the police station, were eventually asked to leave.

Police officers at the station were furious about what they described as the preferential treatment of Pistorius.

"He, like everyone here, is a suspect ... a criminal. This preferential treatment with his family being granted access to him stops now.

"Tonight he will eat the same food as his cellmates, sleep on the same mattresses and shower in the same area.

"Other officers, [and] his family, wanted him to have access to a private bathroom at the police station but this is not on. He is a murder suspect and is being treated as such," said a policeman.

Pistorius's advocate, Kenny Oldwage, said his client was coping with his situation.

"He is mentally strong ... obviously, this is an emotional time but he will get over this ... it is just a murder charge he is facing," said Oldwage.