The 46-year-old, accused of murdering 15-year-old Ong Pan Hui, told the High Court on Tuesday that when he squeezed the teen's neck, it did not occur to him then that he would cause her death. Neither did he know how much force he had applied.

Ong said this when he was cross-examined by Deputy Public Prosecutor Amarjit Singh on the fifth day of his murder trial.

The alleged offence took place at his former wife Xiu Yanhong's flat at Marsiling Drive on Oct 20 last year.

Pan Hui, who was strangled, was the daughter of Madam Xiu, 39, from her first marriage in China. Madam Xiu married Ong in 2002 and bore him a son, now five. The couple divorced last year.

Asked by the DPP if he would agree that his stepdaughter did nothing to provoke him into killing her, Ong said he did not know why he was so agitated into pressing her neck that day.

'At that time, she also raised her voice and told me not to disturb her. I was angry with my ex-wife and a little angry with her as well,' he said.

When Ong said he drank too much that day, the DPP said he was just using it as an excuse when in fact he knew exactly what he was doing at the time.

The DPP put to him that he murdered the teen as an act of revenge on his ex-wife for divorcing him and not giving him access to his son. Ong disagreed.

Ong's next witness is Dr Tommy Tan, who will testify that Ong was suffering from severe depression at the time which reduced his mental responsibility for his killing.