A man has been sentenced to a minimum of 32 years' jail after murdering a Perth mother and her 26-year-old daughter at their home in broad daylight.

It is one of the highest minimum terms ever imposed for murder in Western Australia.

Lesley Cameron pleaded guilty to charges of aggravated burglary and murder of Maureen Horstman and her daughter Tamara at their home in the northern Perth suburb of Warwick in December 2013.

In sentencing, Justice Eric Heenan said it was "one of the worst types of murder one can imagine".

"It is the kind of offence which every member of the population dreads because it shows the insecurity and vulnerability of everybody in the community to random crime," he said.

Cameron was 19 when he entered the Horstmans' home through an open door in December 2013.

The court has heard he armed himself with a hammer and went into Tamara's bedroom where he hit her twice to the head.

He then went to Maureen's bedroom and struck her once to the head before returning to Tamara's bedroom and raping her.

Prosecutor James Mactaggart said it was not known whether Tamara was alive or dead when Cameron raped her.

Both women were subsequently stabbed with a pair of scissors before Cameron fled in Tamara's car.

He was arrested the next day outside a house in Mirrabooka.

Intent to kill 'formed suddenly'

Mr Mactaggart said Cameron told police he had knowledge that someone was in the house and he had armed himself with a hammer in case the burglary went wrong.

However, Mr Mactaggart said it was accepted that his intent to kill the women was "formed suddenly and in the heat of the moment".

Lesley Cameron was "drug addled" when he committed the offences, his lawyer told the court. ( Facebook )

Defence lawyer Domenic Brunello described his client as being "drug addled" at the time, and while he had initially denied taking any drugs, he later told police he had taken ice and speed.

Mr Brunello said his client remembered only certain events on the day of the murders and did not have an "independent memory" of forming an intent to kill the women.

He submitted Cameron's actions were a result of "emotional arousal, fatigue, and ... drug intoxication".

"The offences are ghastly and serious, but there was a lack of planning ... it was chaotic offending," Mr Brunello told the court.

He also said Cameron had a "disadvantaged" and neglected upbringing, which he suggested may throw light on how he came to commit the offences.

The court also heard at the time of the murders Cameron described himself as "a walking time bomb".

Outside court, Tamara's twin brother Nicholas thanked police and said he was happy with the sentence.

"However, no sentence will ever be long enough," he said.

He thanked family, close friends and the community for their support and asked the media to respect his privacy.