Calgary psychiatrist Dr. Aubrey Levin faces 21 charges of sexual assault, based on allegations by patients. (CBC)

The Alberta government is quietly trying to find out if there may be more alleged victims of a Calgary psychiatrist already charged with sexually assaulting some patients.

CBC News has learned that Alberta Justice has recently sent out letters to defence lawyers, asking for help from their clients.

Dr. Aubrey Levin, who was used as a forensic psychiatrist by Alberta courts for years, was charged earlier this year with sexually assaulting 21 male patients.

One of the letters arrived at the office of Calgary lawyer Adriano Iovinelli.

"This is the first time in 16 years that we've ever seen [such a letter]," said Iovinelli. "This is unprecedented."

'Significant position of power'

The letter was sent to lawyers whose clients had been ordered by the court to see Levin "on many occasions." It states: "If you have any concerns about Dr. Levin in his professional capacity, you may also wish to contact the Calgary Police Service."

Alberta Justice said that so far, 59 such letters had been sent out.

"Our primary concern is to see that justice is done," said David Dear, spokesman for the ministry. "Was there any chance that in these cases, from what we can find in the file, that there was anything inappropriate … that may have improperly influenced the outcome?"

Alberta Justice has sent out 59 letters to lawyers whose clients were under court orders to see Dr. Aubrey Levin. (CBC)

Levin, 72, was employed by the courts on numerous occasions where those convicted were ordered to see him before a judge passed sentence.

"It's a court-ordered report," said Iovinelli. "So imagine being an accused and you are looking at a further period of incarceration, a significant period of incarceration, and the opinion of this particular doctor may determine that effect.

"It's a very significant position of power."

Twenty-one men have alleged they were sexually assaulted by Levin during court-ordered psychiatric assessments or counselling sessions, either in his office at the Peter Lougheed hospital in Calgary or in examination rooms.

Linked to apartheid electroshock therapy

Levin is not unfamiliar with controversy.

While a colonel in the South African military under apartheid in the 1970s, he was linked to the use of electroshock aversion therapy, now widely discredited, that was supposed to "cure" gays and lesbians of their homosexuality.

Dr. Aubrey Levin isn't new to controversy, having been linked to the use of electroshock aversion therapy on homosexual soldiers when he was a colonel in the apartheid South Africa military. (CBC)

Levin's activities were brought up during South Africa's Truth and Reconciliation Commission, but he was never prosecuted for them.

The Alberta College of Physicians and Surgeons, which licensed him in the 1990s, said Levin remains under suspension until his criminal charges are dealt with.

Calgary police won't say if more people have come forward as a result of the letters sent by Alberta Justice.

Nor will the government say how many more people will be contacted, only that Levin was employed by the courts for nearly 13 years.

A preliminary hearing is scheduled for Levin in June.