Chris Williams, AP

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 important 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.

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. “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 was using the internet to manipulate people into killing themselves.

Last May, a Minnesota task force searched Melchert-Dinkel's computer and found a web chat between him and a young Canadian woman who took her own life 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 obtaining the search warrant for Melchert-Dinkel's computer, Minnesota authorities cited a decades-old, rarely used state law that makes it a crime to encourage someone to commit suicide. The offense carries up to 15 years in prison. The law does not specifically address situations involving the internet or suicides that occur out of state.

George Washington University Law School professor Jonathan Turley, who follows the issue of physician-assisted suicide, said he has never heard of anyone being prosecuted for encouraging a suicide over the Internet. Turley said if prosecutors file charges against Melchert-Dinkel, convicting him will be difficult — especially if the defense claims freedom of speech.