Probing the minds of our most brutal killers

Few people know as much about Hong Kong's most brutal killers as Dr Henry Yuen Cheung-hang.

Since he became a forensic psychiatrist in 1986, he has interviewed and assessed most of the city's most dangerous people.

They have included the city's most notorious serial killer Lam Kor-wan, the Tuen Mun serial rapist and killer Lam Kwok-wai, the mentally ill son who threw his mother's head out of the window of their Aberdeen home; and the 'Hello Kitty' killers, who tortured a young mother to death and stuffed her skull into a Hello Kitty doll.

As the city's most senior forensic psychiatrist, Yuen read their minds and tried to find out why they killed.

He said murderers were not necessarily mentally ill although their behaviour could be extremely cold-blooded and brutal. 'Some killers have a very clear mind. They know exactly what they are doing. We cannot say someone has an illness just because he has some bizarre behaviour. The actions of people who donate all their money to help others could be seen as bizarre behaviour by other people,' Yuen said.

During his career, two people convicted of murder confessed to him, years after their conviction. Both were released after a review of their sentences. But in one case, Yuen really felt he had been duped.