A Canberra man has denied laundering almost $400,000, insisting he won at least half the cash counting cards at casinos.

Key points: Almost $400k in cash found at Chang-Kee Song's home in mid-2016

Almost $400k in cash found at Chang-Kee Song's home in mid-2016 He says he kept cash because he did not trust banks

He says he kept cash because he did not trust banks Song insisted he won at least $250,000 by counting cards

Chang-Kee Song, 43, was charged with trafficking heroin and money laundering after "well-packaged heroin" and cash was found at his home in Canberra's south in mid-2016.

On Friday Song pleaded guilty to trafficking heroin on the third day of his ACT Supreme Court trial but maintained his innocence on a charge of laundering cash.

He admitted he sourced heroin for a friend but he insisted he won at least $250,000 of cash found at his Phillip home.

Song also told the court he had worked two jobs for almost a decade to save the remaining $150,000 which he kept in cash at his home because he was "a bit funny about banks".

He spent several minutes explaining to Justice David Mossop the method he uses to count cards, detailing how he assigns values and calculates the number of decks to inform his bets.

"I like to play Blackjack," he said, telling the court he and a group of friends had learnt the technique when they were younger.

"I gave it a go again, and it worked out quite well."

He said he would gamble at casinos in Sydney and Melbourne because Canberra's casino was small and had installed card shuffling machines which made counting difficult.

"[Casinos] don't like it," he said, describing various ways casinos tried to combat the practice.

Man and friends 'pooled money' to get cheaper drugs

Song admitted to using heroin on and off for the past two decades but said he had fallen into severe addiction in recent years.

He told the court at the time of his arrest he was working at the Fyshwick Markets and had to dip into his savings to support his $500-per-day drug habit.

He said he and some other heroin users had formed a group to pool money and obtain larger quantities of drugs at a cheaper rate.

Song also admitted he obtained heroin for a friend after the woman gave evidence at the trial yesterday that she cleaned his house in exchange for drugs.

"I understand now that that is called trafficking," Song said.

"I wish I hadn't done it. I felt I had to help her."

He told the court he had never become a dealer because "it doesn't sound like a great life" and he had never "been big" on confrontation.

"I understand how it looks," he said, referring to the large amounts of cash at his home.

"It looks bad, but it's not the case."

But the court also heard a series of phone calls from several people arranging to meet Song to pick up quantities of drugs, with one caller telling Song he would "fix you up tonight".

In the calls, Song asked the person "how much they wanted" and told them to meet at bus stops, streets or other landmarks.

Song told the court most of the calls were from members of the group that would purchase heroin together.

The court heard he had been on a methadone program while in prison and was no longer addicted to heroin.

The trial continues.