A delivery driver who failed to convince a High Court judge that he did not know he was delivering drugs has been handed the death penalty after being convicted of drug trafficking.

Mohamed Shalleh Abdul Latiff's defence during a seven-day trial that ended on Jan 28 hinged on the claim that he thought the three bundles he had been tasked to deliver contained contraband cigarettes.

But the bundles were found to contain 54.04g of diamorphine, also known as heroin.

The Misuse of Drugs Act provides for the death penalty if the amount trafficked exceeds 15g.

In her grounds of decision released on Wednesday, High Court judge Hoo Sheau Peng said the accused had failed to successfully rebut the statutory presumption that he knew he was carrying the drugs.

At the end of the trial, Justice Hoo passed the mandatory death sentence on Mohamed Shalleh.

There were no details on the accused's age and nationality.

On Aug 11, 2016, Mohamed Shalleh received a plastic bag and three bundles wrapped in brown paper, packed in separate ziplock bags, from Malaysian Khairul Nizam Ramthan. Each bundle was round, irregularly shaped and about the size of a palm.

Mohamed Shalleh passed the Malaysian man $7,000, which had been given to him by a friend he knew as "Bai", who had arranged the delivery. The men then parted ways in separate cars.

Central Narcotics Bureau (CNB) officers tailed both men and arrested Mohamed Shalleh at Mei Ling Street, where he was due to deliver the goods to a third party. The Malaysian man was arrested at Woodlands Checkpoint.

Mohamed Shalleh maintained he had been delivering contraband cigarettes for Bai, who said it would offset some of the debt that Mohamed Shalleh owed him.

This was the second time Mohamed Shalleh had agreed to help Bai deliver contraband cigarettes.

But Justice Hoo picked at the defence that he had trusted and believed Bai's word that the delivery concerned only cigarettes.

The accused had met Bai in prison in 2008, but lost contact.

They became re-acquainted in 2014 at the Singapore Turf Club in Kranji, where Mohamed Shalleh would place bets with Bai, a "bookie" there. He accumulated at least $7,000 in debt.

They met again at a friend's wedding in 2016, where Bai gave the accused more time to repay his debt.

Among the reasons cited for his trust in Bai, Mohamed Shalleh said he believed the former's claim that he dealt in the business of contraband cigarettes. He added that Bai had not insisted he repay his debt and that their mutual friends had said Bai could be trusted.

As a result, the accused claimed he was not suspicious and did not verify the contents of the goods he was delivering.

Justice Hoo said these points were "weak support" for the strong claim of trust placed in Bai, and noted that during cross-examination, the accused said he did not know basic details about Bai, including his actual name or address.

The accused also claimed the three bundles had been placed inside the plastic bag when he received them, and that he had not seen the bundles until CNB officers searched his car.

However, Justice Hoo noted this ran contrary to the evidence given by CNB's senior staff sergeant Tay Keng Chye, who testified the bundles were found beside the plastic bag on the floorboard of the car.

The judge added that the round and irregular shape of the bundles should have aroused suspicion about the nature of their contents.

When questioned, Mohamed Shalleh insisted he would still believe they contained cigarettes, as it was possible they could have been repacked into smaller packets. However, Justice Hoo found this claim untenable.

In her concluding remarks, Justice Hoo said the covert and complex nature of the delivery should have triggered suspicion as to the value and nature of the goods.

For this to be overlooked, a high degree of trust in Bai would have had to be found. However, this was not borne out by the case evidence.

"Having reviewed the evidence in totality, I found that the accused failed to show any unique circumstances justifying the high level of trust in Bai, and I was unpersuaded that he relied on the information allegedly given by Bai," said Justice Hoo.