The son of the West Australian police commissioner has been fined for unlawfully contacting his ex-partner by sending her abusive and offensive messages on social media.

Russell Joseph O'Callaghan, 34, appeared in Perth Magistrates Court via videolink from the maximum-security Casuarina Prison on Thursday and pleaded guilty to breaching a violence restraining order and breaching protective bail conditions.

The court heard O'Callaghan, who was on Tuesday sentenced to three years and two months behind bars for violent offences against the same victim, contacted her 21 times on Facebook between October 24 and 27, 2014 in the wake of the drug-fuelled attack some two months earlier.

"You're a f***ing maggot ... I'll make sure you get it good," one of the messages read.

Defence counsel Sandra De Maio said O'Callaghan was not stalking the woman as they'd maintained a relationship on Facebook and she had instigated contact on that occasion, asking for money for their son.

Ms De Maio said they had started by professing their love for each other but communications disintegrated when allegations of infidelity arose.

But he pleaded guilty as he understood he was not meant to contact her in any way after her August ordeal, which lasted about two days and included choking her, pulling her hair, sitting on her and holding scissors against her throat.

O'Callaghan, who was previously jailed over his involvement in a clandestine drug laboratory that exploded, was fined $800 and ordered to pay costs of $79.