A Canadian psychiatrist accused of human rights abuses in apartheid South Africa for subjecting gay soldiers and conscientious objectors to electric shock "cures", will stand trial in Calgary on Wednesday for allegedly sexually abusing male patients.

Aubrey Levin, known in South Africa as "Dr Shock" for his use of electroshock therapy, is charged with sexual assaults on 10 patients, mostly prisoners assigned by the Canadian justice system for treatment. On Tuesday, a jury ruled he was fit to stand trial after the defence claimed Levin, 72, was suffering from the early stages of dementia.

Levin was arrested only after a male patient secretly filmed him making sexual advances. Earlier complaints by others were ignored by the authorities or not believed. His licence to practice has been suspended and the Alberta justice department has reviewed scores of criminal convictions in which the psychiatrist was a prosecution witness.

One of Levin's patients told CTV two years ago he endured abuse because he was afraid to protest.

"I didn't want him to write anything negative about me. So I pretty much kept quiet through the whole ordeal and the next time I came forward I was going to bring a tape recorder and record everything he was going to say, just to protect myself," the man said.

After his arrest, about 30 other patients came forward to accuse Levin of sexual abuse.

Levin's arrest raised questions in Canada as to how he was allowed to become a citizen and permitted to practice at the University of Calgary's Medical School even after he was named by South Africa's Truth and Reconciliation Commission (TRC) for "gross human rights abuses" during the apartheid era.

Levin was a colonel in the South African military and chief psychiatrist at 1 Military hospital in Pretoria in the 1970s and 80s, where he was in charge of a unit where electric shocks were administered to "cure" gay white conscripts. Levin also oversaw the use of electroshocks and powerful drugs against conscientious objectors refusing to fight for the apartheid army in Angola or suppress dissent in the black townships, who were held against their will and classified as "disturbed".

Levin, a member of the ruling National party during apartheid, had a long history of claiming to be able to cure gay people. In the 1960s, he wrote to a parliamentary committee considering the abolition of laws criminalising homosexuality saying they should be left in place because he could turn them into heterosexuals with electric shocks, known as aversion therapy. From 1969, he subjected an undetermined number of men to the treatment at the infamous ward 22 of the military hospital near Pretoria that catered for service personnel with psychological problems.

Levin encouraged commanding officers and chaplains to refer "deviants" for electroconvulsive aversion therapy, which consisted of homosexual soldiers being shown pictures of naked men and encouraged to fantasise as they were subject to increasingly powerful electric shocks until they begged for the pain to stop.

Some of the abuses were documented by the Aversion Project in South Africa (pdf). Its report quotes Trudie Grobler, an intern psychologist in the psychiatric unit at 1 Military hospital, who was forced to give electric shocks under Levin's supervision.

"I know that [the psychiatrist] did aversion therapy with the homosexual men. I don't know of a single case where it was successful … You know he would show the boys men, and then shock them, and then show them girls," she said.

According to the Aversion Project report, Grobler also saw a lesbian subjected to such severe electric shocks that her shoes flew off. "I can only think that it was the same method and intensity that the woman had been given. And it was terrible. … I couldn't believe that her body could survive it all," she said.

According to the Aversion Project, some soldiers were subjected to hundreds of electric shock sessions. It said Levin "coerced conscripts into admitting that they were homosexual to their parents, and further coerced them to undergo aversion therapy".

Among them was Michael Smith, then an 18-year-old conscript. Levin forced him to tell his parents he was gay. "It was the first time they realised I was homosexual and they were horrified. Dr Levin told them he had a therapy that would 'reorientate' me, so I agreed to the treatment," he told the Guardian in 2000.

Smith was subject to numerous electric shock sessions.

"When you kind of reached the maximum point and then you'd say 'No, no, no, I couldn't stand it any more', then he would say: 'Now you must think about your girlfriend', and all that sort of off-the-wall statements."

Other conscripts with learning difficulties or suffering from post-traumatic stress disorder from fighting in Angola were also given powerful drugs and subjected to electric shocks. One of them was a soldier who subsequently wrote a book, a Branch of Wisdom, under the pen name Christopher.

"Within 2 days of meeting with Dr Levin, I commenced a series 6 ECTs (Electro Convulsive Therapy) against my will," he wrote.

The TRC heard testimony from a gay soldier who was chemically castrated. It was told that at least one patient had been driven to suicide by his treatment at Levin's hands. The psychiatrist refused to testify before the commission.

Levin also targeted drug users, principally soldiers who smoked marijuana, and conscientious objectors who would not serve in the apartheid military on moral grounds. Some were subjected to narco-analysis or a "truth drug", involving the injection of a barbiturate before the questioning began.

Speaking in 2000, Levin said the drug was used to help soldiers suffering from post-traumatic stress. He said electric shock therapy was a standard "treatment" for gay people at the time and those subjected to it did so voluntarily.

"Nobody was held against his or her will. We did not keep human guinea pigs, like Russian communists; we only had patients who wanted to be cured and were there voluntarily," he said.

While the details of Levin's abuses at 1 Military hospital were widely aired in South Africa, he managed to suppress publication of details about his past in Canada by threatening legal action against news organisations.

Canada admitted other South African medical practitioners accused of human rights abuses, including two who worked with Wouter Basson, known as "Dr Death" for his oversight of chemical and biological warfare experiments that included the murder of captured Namibian guerrillas.