Son of WA's top cop jailed over attack

The son of the West Australian police commissioner has been jailed for more than three years for repeatedly bashing and threatening to kill his former partner in front of their five-year-old son.

Russell Joseph O'Callaghan, 34, had consumed a "staggering" amount of drugs when he attacked the 29-year-old woman in her home in August 2014 while visiting her in the hopes of reconciling.

The WA District Court heard on Tuesday that the pair argued about drug-related text messages O'Callaghan was sending before he assaulted her during an ordeal that lasted about two days.

The prolonged attack included putting the woman in a headlock, strangling her, pulling her hair, sitting on her and holding scissors against her throat.

"I'm going to slit your f***ing throat, bitch," he told her.

"I'm going to kill you. This is the end of your life.

"If I can't be with you then I'm just going to kill you."

The woman suffered injuries including scratches and bruises all over her body.

Defence counsel Sandra De Maio submitted that her client's behaviour was fuelled by his "staggering" drug consumption, which included methylamphetamine, heroin, ecstasy and cannabis.

O'Callaghan told police it was the most drugs he had ever used.

Ms De Maio said he was genuinely remorseful, was committed to addressing his drug addiction and had the support of his father, Karl O'Callaghan.

The commissioner did not attend court, but provided a reference for his son.

Judge Linda Petrusa said O'Callaghan had "terrorised" the woman.

"She was entitled to feel safe in her own home and in your presence."

The judge said domestic violence was difficult to detect and hard to prosecute.

"This offending was serious, it occurred in a domestic setting, it was perpetrated against a vulnerable victim, it was persistent and occurred over a protracted period."

Judge Petrusa also warned O'Callaghan he was at risk of reoffending if he did not address his drug addiction.

O'Callaghan was sentenced to three years and two months in prison, and will be eligible for parole after serving 19 months behind bars.

With time already served, he could be free after about five months.

O'Callaghan was previously jailed over his involvement in a clandestine drug laboratory that exploded.