A boy charged with spearing Sydney teenager Liam Knight with a metal rod during a birthday party has been denied bail.

The 16-year-old wept in Bidura Children's Court in Glebe during his appearance.

The court heard the boy and his cousin were among a group of alleged gatecrashers who arrived at an 18th birthday party at a home in the northern Sydney suburb of Forestville on Friday.

Prosecutor Sgt Gabrielle Coombs said the alleged offender's cousin had told police the accused was the one who threw the metal rod.

But the boy's lawyer Gregory Stanton said the boy's alleged accomplices were attempting to deflect attention from themselves.

"He is possibly being fingered by persons allegedly involved in this offence," Mr Stanton said.

Magistrate Elizabeth Ellis said that although police said they had three independent witness accounts of the boy's actions during the incident those statements were not available in court.

She said the case was "weaker" rather than "stronger".

Reporters outside the court were abused by the boy's mother, who was visibly distressed as she left the building.

Liam remains in a coma in North Shore hospital.

A metal rod penetrated his head so deeply part of it had to be cut off at the scene before he could be transported to Royal North Shore Hospital where doctors surgically removed the rest of the rod.