Woman dies after Perth court stabbing

A woman has been stabbed to death allegedly by a man who knew her inside a court building in Perth's northern suburbs.

The woman, aged in her 30s, is understood to have been stabbed in the neck, hitting an artery, at about 10am at the Joondalup Justice Complex.

A 40-year-old man was arrested at the scene and was being questioned by police.

Janet Lee, who was present at the court, told the ABC the attack had occurred in a mediation room that she was sitting outside.

Screams were heard, staff were seen running to get towels and to help and a man was sitting on the floor surrounded by security.

First aid attempts were made and paramedics took the woman to Joondalup hospital but she could not be saved, WA police acting Inspector Andrew Maher told reporters.

"A 40-year-old man who is known to the victim is in police custody," he said.

The police union were quick to release a statement saying they had warned authorities for years about the lack of security at court complexes and the need to remove the law banning police officers from carrying guns.

Courts in Perth's CBD have airport-style security screening but suburban courts have nothing, other than guards, enabling people to carry weapons.

WA Police Union president George Tilbury said the organisation's worst fears had been tragically realised.

"Sadly, a woman has lost her life in an event that could have been prevented if appropriate security was in force, including the use of metal detectors at the court entrance."