Nagaenthran, 34, was hanged yesterday after being found guilty more than a decade ago for trafficking at least 43gm of heroin into Singapore in 2009. Multiple appeals over the sentence had been dismissed in the city-state’s courts.

Lawyers for the Malaysian, along with the United Nations Human Rights Office and businessman Richard Branson, had urged the Singapore government to halt the execution, arguing he was intellectually disabled after being assessed by a court-appointed psychologist in 2013 to have an IQ of 69.

Singapore’s Central Narcotics Bureau said in a statement the courts had found that “Nagaenthran knew what he was doing, and that he did not suffer from intellectual disability”.

“There has been much misinformation that has been put out in relation to Nagaenthran, in particular on his mental state,” the agency said, pointing to two cases in the US in 2021 in which those executed had IQs in a similar range.

While Singapore has moved away from imposing capital punishment for some crimes, it maintains its tough stance on drug trafficking and manufacturing-related crimes.

Malaysia, where a moratorium on drug-related executions has been in place since 2018, also appealed to Singapore’s authorities to halt the execution.

In a statement on April 25, the United Nations Human Rights Office expressed concern about “a rapid rise in the number of execution notices issued since the beginning of the year in Singapore”.