Minneapolis ? A nurse who authorities say got his kicks by visiting Internet suicide chat rooms and encouraging depressed people to kill themselves is under investigation in at least two deaths and could face criminal charges that could test the limits of the First Amendment.

Investigators said William Melchert-Dinkel, 47, feigned compassion for those he chatted with, while offering step-by-step instructions on how to take their lives.

“Most importatn is the placement of the noose on the neck … Knot behind the left ear and rope across the carotid is very important for instant unconciousness and death,” he allegedly wrote in one Web chat.

He is under investigation in the suicides of Mark Drybrough, 32, who hanged himself at his home in Coventry, England, in 2005, and Nadia Kajouji, an 18-year-old from Brampton, Ontario, who drowned in a river in Ottawa, where she was studying at Carleton University.

While the victims’ families are frustrated that no charges have been filed, legal experts said prosecuting such a case would be difficult because Melchert-Dinkel didn’t physically help kill them. In the meantime, he has been stripped of his nursing license.

“Nothing is going to come of it,” Melchert-Dinkel said of the allegations during a brief interview with The Associated Press. “I’ve moved on with my life, and that’s it.”

The case came to the attention of Minnesota authorities in March 2008 when an anti-suicide activist in Britain alerted them that someone in the state was using the Internet to manipulate people into killing themselves.

Last May, a Minnesota task force on Internet crimes searched Melchert-Dinkel’s computer and found a Web chat between him and the young Canadian woman describing the best way to tie knots. In their search warrant, investigators said Melchert-Dinkel “admitted he has asked persons to watch their suicide via webcam but has not done so.”

Authorities said he used such online aliases as “Li Dao,” “Cami” and “Falcon Girl.”

The Minnesota Board of Nursing, which revoked his license in June, said he encouraged numerous people to commit suicide and told at least one person that his job as a nurse made him an expert on the most effective way to do it.

The report also said Melchert-Dinkel checked himself into a hospital in January. A nurse’s assessment said he had a “suicide fetish” and had formed suicide pacts online that he didn’t intend to carry out.

In excerpts of a Web chat between Kajouji and Melchert-Dinkel, provided by Kajouji’s mother, he allegedly gave the young woman both emotional support and technical advice on hanging.

“im just tryin to help you do what is best for you not me,” one message said, posted using the alias “Cami.”