A key witness in Oscar Pistorius’s murder trial has wept in court, saying she still relives the “terrifying screams” heard from his home the night Reeva Steenkamp was killed.

In vivid testimony that cast doubt on the star sprinter’s defence, Michelle Burger, her husband and a third neighbour each told the court that they heard a commotion then gunshots on Valentine’s Day 2013.

The trio’s account directly contradicts Pistorius’s claim that he shot the 29-year-old model and law graduate Steenkamp through a locked toilet door after mistaking her for an intruder.

In an emotionally charged second day of the South African Paralympian’s trial, Burger broke down in the witness box on Tuesday after fierce cross examination, saying events of that February 14 still haunt her.

“When I’m in the shower, I relive her shouts. The terrifying screams,” the university lecturer said, her voice cracking with emotion.

Another neighbour, Estelle van der Merwe, who lives less than 100 metres from Pistorius’s home, said she heard arguing coming from the house when she woke just before 2am.

“It lasted about an hour,” she said, adding later that she recalled waking up to the sound of loud bangs.

Burger’s husband, Charl Johnson, also took the stand, telling judge Thokozile Masipa that a woman’s screams woke him up and that he ran to his balcony, less than 200 metres from Pistorius’s home.

“At that point the fear and intensity of her voice escalated and it was clear that this person’s life was in danger,” he said.

“That’s when the first shots were fired,” although Johnson could not recall how many.

Both Johnson and Burger also said they heard a male person shout for help, a point that was seized upon by the defence as evidence Pistorius was calling for help.

Pistorius, 27, a double amputee known as the “Blade Runner” for his carbon-fibre running blades, has pleaded not guilty to murder and three unrelated gun charges.

While admitting killing Steenkamp, the sprinter described it as a “tragic accident”, denying murderous intent and saying “we were in a loving relationship”.

If found guilty of premeditated murder, Pistorius faces 25 years in South Africa’s notoriously brutal jails and an abrupt end to his glittering sporting career.

In the face of the prosecution’s onslaught, Pistorius’ lawyer Barry Roux spent most of Tuesday trying to pick apart the witnesses’ account of events.

In terse exchanges, he accused Burger of rejecting Pistorius’s account out of hand, moulding her testimony to fit media reports and jumping to conclusions.