Singapore's highest court denied a mentally challenged Malaysian man's last-ditch appeal against a death sentence on Tuesday, leaving his family "devastated" and "shocked" by the decision.

Nagaenthran K. Dharmalingam, 34, was caught in 2009 for bringing a minor amount of heroin-one and a half ounces into the state of Singapore, which has some of the strictest drug prohibitions in the world.

His death sentence was planned for November, but his lawyers have maintained that imposing the death sentence on a mentally ill person violates international law.

The Court of Appeal, however, dismissed the case, stating that it had "no factual and legal basis," and that local legislation takes precedence over international law.

Nagaenthran had been "afforded due process," and his defense had presented "nothing forward to suggest that he has a case," it claimed, adding that the Malaysian's attorneys were filing "hopeless" applications after multiple appeals had previously been denied.

A human rights lawyer involved in the case said no more appeals would be filed and Nagaenthran could be executed within days.

His sister, Sarmila Dharmalingam spoke to AFP, expressing, "We are shocked by the court decision despite my brother... having a low IQ."

Nagaenthran is said to have an IQ of 69- a recognized level of mental disability.

Travesty of justice

Reprieve, a non-governmental organization that advocates against the death sentence, stated that hanging Nagaenthran would be a "travesty of justice" and would violate Singapore's obligations to promote the rights of the disabled.

Maya Foa, the director of the organization, urged President Halimah Yacob to "listen to the cries for mercy within Singapore and around the world... and spare  the life of this vulnerable man."

Singapore has not executed anyone since 2019 but has been raising concerns due to planned executions in the near months.

According to Amnesty International, Singapore is one of over 30 countries that still implements the death penalty for drug-related crimes and murder, alleging that it keeps the country one of the safest in Asia.

Authorities defended the death sentence for Nagaenthran by claiming he was fully aware of his actions at the time he committed his offense.