Dramatic security camera footage has been played to the Supreme Court showing the moments before and after a Perth man allegedly fatally stabbed his former partner at the Joondalup court complex.

Key points: Paul Turner allegedly fatally stabbed his former partner Sarah Thomas during a meeting

Paul Turner allegedly fatally stabbed his former partner Sarah Thomas during a meeting Ms Thomas suffered six stab wounds, including three to her neck, and died almost immediately

Ms Thomas suffered six stab wounds, including three to her neck, and died almost immediately A WA court has been shown footage of the minutes surrounding Ms Thomas's death

Paul Gary Turner, 43, is on trial accused of murdering the mother of two of his children, 33-year-old Sarah Thomas, in December 2016.

It is alleged Mr Turner smuggled a knife into the meeting, which was being held in the presence of a court registrar to discuss money he claimed he was owed by Ms Thomas.

The trial was told when Ms Thomas said she was not going to offer him anything, Mr Turner retrieved the knife — which he was allegedly hiding in his pocket or in a file he was carrying — and stabbed her six times, causing injuries the court was told could not be survived.

Sarah Thomas is the mother of Paul Turner's two children. ( AAP/Supplied )

The footage shows Mr Turner waiting for the meeting to start, with prosecutors alleging he repeatedly puts his hand in his pocket because that is where he may have hidden the knife.

He then walks into the room followed by Ms Thomas.

About five minutes later the registrar rushes out, followed by Mr Turner who sits on the floor before security guards and police rush to the scene.

He is eventually handcuffed and led out of the building by police.

Paul Turner waits for a meeting with his former partner Sarah Thomas. ( Supplied: WA Supreme Court )

The trial also heard evidence from forensic pathologist Clive Cooke, who conducted the post-mortem examination on Ms Thomas's body.

He told the court one of the three wounds to her neck was the "lethal" injury.

Dr Cooke said the wound had "totally divided" her carotid artery, which carries blood to the brain, and was "non-survivable" even if medical attention had been available.

Accused killer had 'commando' knife training

The court has heard that about a decade earlier Mr Turner did martial arts training, which included learning how to use "commando knife skills" to inflict fatal injuries on the human body.

It is alleged he used that training to deliberately and intentionally stab Ms Thomas.

On Thursday Mr Turner's lawyer, Lisa Boston, admitted her client had trained in commando knife techniques, in particular those of WE Fairbairn — a British paratrooper who developed hand-to-hand combat methods.

Paul Turner is alleged to have used this knife to kill his former partner. ( Supplied: Supreme Court of WA )

The court was shown a document called "the Fairbairn-Sykes fighting guide" which outlined stabbing techniques and what was called "a timetable of death".

A statement was also read from a man who was now dead but who had trained Mr Turner, including in "weapons awareness techniques".

Mr Turner has pleaded not guilty to the murder charge.

The trial is set down for nine days.