A father wants compensation for the death of his son who died in June in a Beijing mental hospital five days after he was sent there by police.

The father is basing his case on an autopsy, which showed his 20-year-old son died from an overdose of a medicine used for treating severe mental illness.

The autopsy of Hao Lei showed that the mental hospital, a branch of the Huayi Hospital in Changping district, treated him as a severe patient before diagnosing what kind of mental illness Hao had.

"He could never be mentally ill, or else we wouldn't let our only son go to the city to work by himself. Besides, none of our family members have ever had mental problems," said the father, Hao Husheng, a farmer from Mahe village of Luonan county of Northwest China's Shaanxi province.

In an interview with China Daily on Monday, the father insisted that the police had sent his son to the mental hospital mistakenly.

According to Hao Husheng, Hao Lei left home in April to find work in cities, and went to Beijing in June. He contacted his family only once, on June 19.

One night, Hao Lei refused to get off a bus because he was homeless and scared. The bus station later called the police, and the police took him away, the police told the father.

"My son cannot speak standard Mandarin. Maybe that's why the police thought he was babbling and decided he had mental problems," the father said.

The police record shows that "the man with unsound mind was babbling".

The hospital record shows Hao Lei was sent there in the early morning of June 21, escorted by two policemen. He died in the hospital five days later.

"Nobody told us that he was sent to the mental hospital, neither the police nor the hospital," Hao Husheng said. "It took them only three hours to find us after he died, but nobody contacted us previously."

Hao Husheng wanted to know the real reason for his son's death so he asked for an autopsy. "In October I got the autopsy report, which said that my son died of misdiagnosis and overdose," he said.

Both the Huayi Hospital's mental branch and Shibalidian police station that had sent Hao Lei to the hospital refused to comment on Monday.

"He died of adverse reaction to the medicine, and it should not be counted as a medical accident," Ouyang Xiuge, vice-president of the hospital, was quoted by Beijing News as saying.

Hao Husheng said the director of the police station admitted that they had some responsibility for the death, and he gave Hao Husheng 5,000 yuan ($752) to pay the hospital bill.

Zhang Shuliang, Hao's lawyer, said: "We want the hospital to pay 600,000 yuan as compensation for the wrong diagnosis and prescription."