After strangling Lao, Lam told his brother to take care of their mother and study hard before he plunged a pair of scissors into his own neck, the trial heard. Lam survived the suicide attempt at his family's flat on the Wah Ming Estate in Fanling.

Lam admitted strangling Lao but pleaded not guilty to murder, saying he had not meant to kill the woman. The prosecution rejected his offer to plead guilty to manslaughter.

Lam's trial heard that police found a note in his trousers that said: 'Wife, I really love you a lot. I cannot be without you.'

Lam's half-brother, a Form Seven student, said he had been playing computer games in their flat when the killing happened.

He saw Lao leave the bathroom and go into his brother's bedroom. Shortly after 3pm, Lam came out of the bedroom.

'He said to me, 'Study hard, take good care of mother',' Lam's brother told the court. 'He seemed to be in a desperate state.'

Thinking that his brother's comments were odd, Lam's sibling knocked on the door several times.

Lam told him to go away. The younger brother then kicked open the door and found the couple on the bed, with Lao looking pale and Lam with scissors protruding from his throat.

Their mother, Suen Wai-chai, 52, said Lam and Lao, who had been living at the flat on and off for more than a year, had woken her when they had quarrelled days before. Lao had been chatting with another man on the phone, the trial heard.

Yesterday, the court heard that Lam had been released from prison after serving a term of four years and eight months for robbery.