'This is a man who has failed to grasp opportunities ... and seems to be unable to get out of the vicious circle of returning to prison again and again,' Mr Percy said.

Choi was arrested on January 21, just five months following his release after serving another sentence for drug trafficking. He was stopped by police during a sweep of Wah Lok Building on Yim Po Fong Street in Mong Kok.

When told he would be searched, he replied: 'Ah sir, there is no need for searching. I will take out the white powder myself.'

He removed three packets of drugs from his underwear and another that was strapped to his leg. Those packets contained 44.42 grams of pure heroin hydrochloride.

After being arrested, Choi was taken to his flat, where he pointed out a drawer in which the police could find more heroin and implements for breaking it up into individual deals.

The 281 grams of white powder found in the drawer contained 147.11 grams of heroin hydrochloride.

The drugs were estimated to have been worth about HK$194,000 at the time of the seizure.

Mr Percy told the court that his client had been as helpful as possible to police and was aware he was facing a significant sentence. He had tried to find work but, due to his age, criminal record and lack of education, was forced to turn to welfare.

Choi chose to stay in Hong Kong rather than return to Guangzhou to live with his wife, 19-year-old son and 92-year-old mother, Mr Percy added.

Mr Justice Peter Nguyen said it was tragic that Choi was unable to escape the cycle of addiction and criminality he now found himself in. His situation was worsened by his poor level of education and the fact that he had spent most of the last three decades in prison.

However, the judge said, heroin trafficking was a very serious offence and the courts were obliged to hand down severe penalties for those who engaged in the trade.

After taking into account his guilty plea, he sentenced Choi to seven years and eight months.

David Cheung, supervisor of Caritas Wong Yiu Nam Centre, which aids adult drug abusers, said being jailed might be the most effective method to help them in some cases.

'Some drug abusers behave very well and manage to stay away from drugs when they are admitted to a rehabilitation centre or are jailed, as the drug supply is totally cut off. But once they are released, they will quickly take drugs again,' he said.

'It really depends on the individual - does he or she want to make changes for a better life? This might be a simple question for most people, but it is a tough one for drug abusers.'