But lawyers for Matthew James Massey, 40, argued he deserved another chance to redeem himself after spending more than two decades behind bars.

Massey pleaded guilty in the ACT Supreme Court to peddling 7.2 grams of methylamphetamine to a police officer during a crackdown on illicit drug supply in January 2013.

Justice Richard Refshauge on Monday acknowledged the difficulty he faced in sentencing Massey, given his lengthy criminal history, and accepted "massive amounts of jail time" would not be in his favour.

He asked Massey's defence barrister Alyn Doig: "How do we address this?

"The fact is, he's been unable to stop committing serious offences, in some cases very serious offences.

"It's just Greek tragedy."

Mr Doig said Massey was well known to the court and wider community, but he urged the judge to consider the objective seriousness of the single offence in sentencing.

He pushed for the judge to consider a suspended term of imprisonment.

"Society has a responsibility, the system has a responsibility to Mr Massey and he has not been assisted in this situation ... Mr Massey is not the devil incarnate."

"He's been a very bad person over a long period of time but he's not beyond redemption."

Mr Refshauge said the lawyer's arguments fell on "fertile ears" but "I don't have the resources to do what you're saying".

"The system at the moment has not provided any mechanism. If I release him, what supports does he have?" he said.

Massey, who had sought help for drug addiction, told the judge he wanted to move in with his partner at Giralang if released and his number one priority was to be a role model for their baby son.

Justice Refshauge: "Do you have the strength of character to do that?"

Massey: "Yes I do, your Honour."

Mr Doig said Massey had been dating former basketballer turned drug addict Janna Sladic, who died from a suspected heroin overdose last year, around the time of the offence and was well aware of her fate.

"He's not stupid, your Honour. He's not clever, but he's not stupid.

"He's looking for some mercy to be tempered here, if your Honour pleases."

Mr Doig said his client regretted the waste of life his time in jail had been and knew he faced his last chance to turn his life around.

"He's got a decision to make: Is he going to work hard to stay free and clean, or is he going to go back and die in prison?"

Prosecutor Katrina McKenzie said Massey's long history of violent offending showed his prospects for rehabilitation were bleak.

"He has a son now, he's got two other children and they've never provided an incentive to get on the straight and narrow," she said.

"Any period in the community puts the community at risk, whether it be from dealing drugs or committing acts of violence."

She pushed for the judge to impose a term of imprisonment without a non-parole period.

Justice Refshauge will hand down his sentence next week.