Magistrate Bernadette Boss has been asked to determine whether Jermaine Goolagong is fit to plead to a string of charges ranging from car theft and aggravated burglary to drug possession.

The ACT Magistrates Court has heard the 19-year-old has an IQ of just 59, equivalent to that of a 10-year-old, and was given a diagnosis consistent with mild-to-moderate mental retardation.

But the prosecution has questioned how the accused car thief was able to pass a learner driving test, correctly answering 34 out of 35 questions on the first attempt and obtain a licence. It is alleged the same licence was later left under the driver's seat of a Porsche Boxster stolen from a home in Kingston last July.

Police have alleged Goolagong's fingerprints were also found on the inside of the car's window and on a stolen iPad found in a Subaru Impreza taken during the same burglary. A second Porsche was also stolen.

Goolagong was released on bail but soon found himself back in court facing fresh allegations of getting behind the wheel, in breach of his bail, and crashing into another car.

The prosecution says his driving test results undermine his claims that he is unfit to plead.

The teenager told consulting psychiatrist Anthony Barker he passed the driving test with the help of three other young people, who gave him answers, and a supervisor. But the supervisor refuted the claim, saying no one else was in the room when Goolagong took the test.

Prosecutor Shane Drumgold said that ultimately it was up to the court, not psychiatrists, to decide whether Goolagong was fit to plead.

Dr Boss said the key issue was whether Goolagong could satisfactorily instruct his lawyers, with ''scaffolding'' in place during the legal process, should the case go to hearing.

The magistrate is due to hand down her decision next month.