There were emotional scenes in a Sydney court today when a woman broke down after her son entered the room in prison greens, cuts to his face, and a swollen left eye.

Lisa Fenney cried when her son Rory Constantino faced Liverpool Court for the first time since he was charged with assaulting an undercover police officer yesterday morning.

Mr Constantino, 27, is accused of arming himself with a steel spear and stabbing Constable Jacob Vella, who was trying to arrest his father Rick, 58, for failing to appear in court on an unrelated matter last week.

Mr Vella, 24, who has worked as a NSW Police officer for two years, had emergency surgery at Liverpool Hospital after sustaining deep wounds to his wrist and neck.

Constable Vella, who is also a personal trainer, is expected to be discharged in the coming days, but it is unclear if he will return to his job at Liverpool Police Station.

Rory Constantino mouthed "I love you" to his mother when he appeared in court. ( Supplied: Facebook )

Rory Constantino blew kisses and mouthed the words, "I love you" to his mother, and his two sisters when he was formally refused bail in court.

Outside court, Ms Fenney walked out in the arms of friends and said: "I was very upset to see him like this, he's a good boy."

Rory Constantino's lawyer said his client would be applying for bail within the next few weeks.

The lawyer also said Rick Constantino was likely to make a bail application.

Rick Constantino was also dressed in prison greens when he faced Liverpool Court on similar charges to his son, including assaulting an officer in the execution of duty.

The father and son will remain behind bars until their case returns to court on June 24.