A young mother accused of killing her child in a car crash will remain behind bars after her lawyer did not apply for bail.

Aneshia Daisy Case, 23, did not appear in Brisbane Magistrates Court when her matter was mentioned today, four months after her three-year-old son Caden died at a police station.

Case and the boy’s father Samuel Ian Paterson, 24, have both been charged with manslaughter and drug trafficking following Caden’s death.

Caden Case died in the foyer of Beenleigh Police Station. (Nine)

Their son was critically injured after the family’s white Mazda veered off the road and crashed in bushland north of the Gold Coast on October 25.

A witness saw the car swerve off the road, before rushing the mother and Caden to Beenleigh Police Station.

Officers at the station attempted CPR but the boy who suffered critical head injuries couldn’t be saved, police said.

Paterson is accused of fleeing the accident and later being found at a nearby address with a one-year-old boy who was uninjured in the crash.

Police will allege Case was behind the wheel at the time of the accident but have refused to comment on the fatal crash’s cause, saying the investigation was “extremely complex”.

Case was not required to appear when her matter was mentioned today.

Magistrate Julian Noud was told by Case’s solicitor Skye O’Dwyer that there would be no bail application.

Samuel Ian Paterson has been charged. (Nine)

Case was also charged with driving without a licence, possession of anything used in a crime and drug trafficking.

Some of Case’s charges arose from the Beenleigh jurisdiction and others from Southport, Ms O’Dwyer said.

“It may be prudent to split them at this early stage,” she said, with the police prosecutor consenting.

Police earlier alleged the mother and children had travelled from the Gold Coast to collect the father from a Beenleigh address before the crash.

Detective Acting Inspector Kent Ellis earlier told reporters the investigation had involved a forensic reconstruction of the crash and analysis of physical evidence along with CCTV footage.

“Determining who was driving at the time of impact required an extensive amount of investigative work,” he said.

Mr Noud ordered Case’s manslaughter and unlicensed driving charges be next mentioned at Beenleigh on March 9.

Case was remanded in custody and excused from appearing in person on her next court date.

Her drug trafficking and another charge were moved to Southport.

Paterson has been in custody since the crash after facing separate charges.

He was remanded in custody to seek legal representation ahead of his next court appearance on March 30.

The father was separately charged with domestic violence offences in October, when his emotional family claimed he would never harm his children.

“We are sick of the f***ing lies,” the boy’s grandfather yelled at the media after the father’s appearance at Southport Magistrates Court in October.