On the morning of 22 November 1990, at 7.15am, a lecturer discovered one of his senior colleagues lying dead on the seventh floor corridor outside his office at the Dover Road campus of Singapore Polytechnic.

The police also noticed a blood trail coming from the victim's body, and followed the bloodstains to the female toilet on the sixth floor.

The young bespectacled man was wearing only a pair of white shorts, and two bags were seized from the toilet; one of them contained a bloodstained shirt and a knife.

[3][4][5] The brutal killing of Tan brought shock to his brother and many people present at the campus, and it disrupted the lessons of many students at the polytechnic.

The school staff of the polytechnic also stated that they would introduce the necessary measures to tighten the security on the campus to prevent similar incidents from happening.

Lee enrolled in Singapore Polytechnic, where he studied before he graduated with a diploma on electronics and communication in early 1990, a few months before he allegedly killed Tan.

[21] Two years after Tan Chin Liong was murdered, his killer Lee Teck Sang was officially brought to trial at the High Court on 5 October 1992.

Lee was represented by Ram Goswami, and the prosecution led by Han Cher Kwang, and the trial was presided by veteran judge T S Sinnathuray, who was best known for sentencing Adrian Lim and his two accomplices to the gallows for the ritual killings of two children at Toa Payoh.

One of them, Corporal Azman Abdul Aziz of the Singapore Police Force, testified that he was the first to discover the blood trail that started from the location of Tan's dead body and led to the toilet where they found Lee, who surrendered to the officers upon their arrival.

Professor Chao testified that out of the three stab wounds, one of them was inflicted on the chest and had penetrated the heart, and this injury resulted into an excessive loss of blood, which was sufficient to cause the death of Tan within minutes.

Eventually, Lee ran out of money, and he could not ask his mother or siblings for help since they were notified of his desertion and attempted to get information from him about his whereabouts each time he contacted his family.

[30] On behalf of these findings, Justice Sinnathuray found 22-year-old Lee Teck Sang guilty of murder, and sentenced him to death.