Jermaine Goolagong, 19, is facing a string of charges relating to a break-in, and the theft of a series of luxury cars, including two Porsches, a Nissan Skyline and a Subaru Impreza WRX.

While on bail, he allegedly broke a court-ordered driving ban, ran a red light, mounted a traffic island and ploughed into a car.

He allegedly jumped out of the car and fled the scene, managing to avoid police for more than a week.

The ACT Magistrates Court ruled Goolagong unfit to plead to the charges on Thursday morning.

The court had previously heard the defendant had an IQ of just 59, and was given a diagnosis consistent with mild-to-moderate mental retardation.

That gave rise to fears he would be unable to satisfactorily instruct his lawyers.

The prosecution argued he was fit to plead, pointing to the apparent ease with which he passed a learner driving test. Goolagong correctly answered 34 of 35 questions on the test on his first attempt, the court heard earlier.

The teenager later told a psychiatrist that he was helped by three other young people and a supervisor during the test.

Those claims were later denied by the supervisor.

The ruling by Magistrate Bernadette Boss means the matter will now go before a special hearing later this year.

Dr Boss also ruled Goolagong was unfit to consent to a forensic procedure, and that he wouldn't understand the general effect and purpose of such a procedure.

The matter will come before the courts briefly next month.

Goolagong remains on strict bail.