A SELF-described drug mule has been handed a jail sentence for what was temporary possession of a large amount of methylamphetamine.

Police patrolling Toowoomba's CBD had spotted Scott Anthony Garner walking on a side street just before midnight on December 10 last year, the city's Supreme Court heard.

Seen to crouch behind a bush, police approached and found the then 33-year-old with a black case containing clip seal bags and methylamphetamine, prosecutor Cameron Wilkins said.

The substance found weighed 11.105g of which 8.389g was pure drug, the court heard.

Garner told police he had been given $900 by a third party, who he owed money, which he was to take to a park where he would meet another person from whom he would take possession of the black case.

He was then to bring the case back to the third party who had promised him 3.5g of drug, the court heard.

He had been returning the case to the third party when intercepted by police.

Mr Wilkins said although Garner had a criminal history, he had no previous convictions for drug offences.

Defence barrister Steve Kissick said his client had a long-standing drug addiction for which he accepted he needed help.

His client and his then de-facto wife had experimented with methylamphetamine some years ago and his client had become addicted, he said.

The now 34-year-old had spent 150 days in custody during which time he had done drug rehabilitation courses, Mr Kissick submitted.

Justice Martin Burns said the case was "unusual".

"You described yourself to police as a 'mule' and I think that is an accurate description," Justice Burns told him.

Garner was sentenced to 18 months in jail but released on parole immediately.