NUS Law Asst Prof Marcus Teo represents applicants in constitutional challenge to Misuse of Drugs Act

In Singapore, any person proven to be in knowing possession of more than a specified quantity of controlled drugs—such as 2g of heroin—is presumed to possess it for the purposes of trafficking, unless it is proven otherwise. Does this presumption infringe the Constitution?

NUS Law Assistant Professor Marcus Teo ’18, a public law expert and practising lawyer, argued before a rare five-judge coram of the Court of Appeal on 7 May 2025, presenting his stance on a landmark constitutional challenge to provisions in the Misuse of Drugs Act (MDA).

At the heart of the case is a critical question: whether statutory presumptions that shift the burden of proof to the accused are consistent with Article 9 of the Constitution, which protects the right to life and liberty. The MDA contains such presumptions relating to elements of the offence of drug trafficking, such as the accused’s knowledge of the nature of the drugs in his possession, as well as his intention to traffic in those drugs.

Representing four individuals on death row, Assistant Professor Teo argued that the presumptions in the MDA are inconsistent with the presumption of innocence and the fundamental rules of natural justice, as they satisfy elements of offences which the prosecution cannot otherwise prove. He also argued that the MDA presumptions deprive accused persons of their life or liberty, contrary to Article 9.

The five-judge panel, led by Chief Justice Sundaresh Menon, underscored the constitutional importance and complexity of the issues raised. The court has reserved judgment following over three hours of detailed arguments, with its decision to be delivered at a later date.

Assistant Professor Teo said, “I believe that legal scholarship and practice enrich each other. The Constitution is the fundamental law of our land and must be treated as such, both in theory and in reality. That, as our Court of Appeal has reasoned, is how people may be given the ‘full measure’ of their fundamental rights. Upholding the Constitution involves the work of many: Parliament, the Government, judges, prosecutors, defence counsel, legal academics, and society at large. It has been my honour to contribute to this process.”

Assistant Professor Teo’s appearance in this case reflects his legal expertise and advocacy skills, as well as NUS Law’s broader commitment to scholarship that engages with real-world legal practice.  Assistant Professor Teo teaches and does research in public law and the conflict of laws at NUS Law, and was recently selected to be emplaced on the Young Independent Counsel Scheme for a period of one year, spanning 2025. Young Independent Counsels are independent third parties that courts can call on to assist in deciding novel or important issues of law that arise in litigation.

Assistant Professor Teo has also written extensively on public law in Singapore and English law. Recent publications include:

• “Denouncing the ‘One Voice’ Doctrine” (2025) 45(1) Oxford Journal of Legal Studies 26-54
• “Administrative Expertise and Wednesbury Unreasonableness” (2025) Public Law 359-384
• “Refining Reasonable Classification” (2023) Singapore Journal of Legal Studies 83-112