But the police say the nurse, who sometimes called herself Cami and described herself as a young woman, was actually William F. Melchert-Dinkel, a 47-year-old husband and father from Faribault, Minn., who now stands charged with two counts of aiding suicide.
Mr. Melchert-Dinkel, whose lawyer declined an interview request on his behalf, told investigators that his interest in "death and suicide could be considered an obsession," court documents say, and that he sought the "thrill of the chase." While the charges stem from two deaths -- one in Britain in 2005 and one in Canada in 2008 -- Mr. Melchert-Dinkel, who was indeed a licensed practical nurse, told investigators that he had most likely encouraged dozens of people to kill themselves, court documents said. He said he could not be sure how many had succeeded.
The case, chilling and ghoulish, raises thorny issues in the Internet age, both legal and otherwise. For instance, many states have laws barring assisting suicide, but rarely have cases involved people not in the same room (much less the same country) or the sharing of only words (not guns or pills).
The case also brings up questions about the limits of speech on the Internet: How does one assign levels of culpability to someone who shares thoughts with people who say they are already considering suicide? And for some who counsel against suicide, it points to a growing area for worry, an online world where the most isolated and vulnerable might be touched in a way that they would not have in the past.
Groups that work to prevent suicide compare suicide chat rooms to "pro-ana" sites, Internet sites that portray anorexia as a lifestyle as opposed to a disease. Anti-suicide advocates say that there has been more than one instance recently where a person killed himself on a Webcam as others watched. Papyrus, a charity in Britain that works to stop young people from killing themselves, says it has tracked 39 cases in that country alone where young people committed suicide after visits to "pro-suicide" chat rooms.
It was the untrained, unpaid Internet sleuthing by Celia Blay, a 65-year-old from a tiny community in Britain, that helped lead to charges in April against Mr. Melchert-Dinkel. "He was practically invisible," she said. "I tried to talk to any police I could, and most of them would have nothing to do with it. The first one I talked to told me, 'If it bothers you, look the other way.' And that really bothered me, because by then I was pretty sure people had died."
About four years ago, Ms. Blay, who describes herself as a "computer illiterate," became friends online with a young, depressed woman who had entered into a suicide pact. Ms. Blay persuaded her not to proceed, but the incident sent Ms. Blay searching for the other member of the pact. It was someone who called herself Li Dao, another screen name that the police later said Mr. Melchert-Dinkel used.
Making inquiries on a Web site aimed at people talking about suicide, Ms. Blay said she found at least half a dozen people who had similar pacts with Li Dao, a name that popped up on all sorts of suicide Web sites. She and a friend uncovered Mr. Melchert-Dinkel's name and e-mail address after setting up a sting in which her friend posed as someone preparing for suicide and was, she said, approached by Mr. Melchert-Dinkel.
By then, the police in Minnesota say, Mr. Melchert-Dinkel had already aided the suicide of Mark Drybrough, 32, of Coventry, England. A coroner's report found that Mr. Drybrough, who was suffering from a psychiatric illness, hanged himself from a ladder in his home in July 2005. His computer showed that he had posted a question in a suicide chat room about how to hang oneself without access to something high to tie a rope to, and that Li Dao -- Mr. Melchert-Dinkel, the police say -- had offered details on how to use a door.
In March 2008, Nadia Kajouji, 18, disappeared from her college in Ottawa. The Canadian authorities investigating her disappearance searched her laptop and discovered that she had been talking online with a person who used the screen name Cami. In e-mail messages, the authorities say, the pair agreed to a pact in which Ms. Kajouji would jump from a bridge into a river (to avoid, at Cami's suggestion, the police say, creating a mess) and Cami would hang herself a day later. In April 2008, Ms. Kajouji's body was found in the Rideau River.
Around the same time, Ms. Blay contacted the St. Paul Police Department through an acquaintance in Minnesota. By then, she said, she had grown frustrated with what she described as the authorities' unwillingness to study the huge file she had amassed with the stories of 20 to 30 people who had been approached online. Over time, she said, she had tried to tell the story to a police department near her home, a member of parliament and even law enforcement in the United States.
Since at least the 1970s, many states have barred assisted suicide, though criminal charges are rarely filed. Physician-assisted suicide is allowed under certain conditions in Oregon and Washington.
In Minnesota, 12 charges of aiding suicide have been brought since 1994, when the state began keeping track, and about half of those have resulted in convictions. That state's law, a felony, applies to "whoever intentionally advises, encourages or assists" another in taking his or her own life; convictions carry sentences of up to 15 years in prison.
Barbara Coombs Lee, the president of Compassion and Choices, who has advocated for laws like the one in Oregon, said she found it "perfectly appropriate" that Mr. Melchert-Dinkel faces such charges. "This is so egregious, so clearly wrong, that I'll be very disappointed if assisted-suicide statutes do not reach this," she said. "There is a bright line between aid in dying and assisting in suicide like this."
Still, legal experts suggested that there may be room for challenges. The Minnesota law itself, some suggested, could be seen as too ambiguous or too broad to include protected speech that falls short of actually leading someone to suicide. The deaths occurred in other jurisdictions, posing potential issues, other lawyers said.
Terry A. Watkins, a lawyer for Mr. Melchert-Dinkel, said it was premature to describe what defense he intends to present but made it clear that he had questions about the law itself, as well as the dissection of causes that lead to any suicide. "As a society, we need to be careful when we start putting together laws that prohibit things like 'encouragement' without a really clear definition of what in God's name you're talking about," he said.
Mr. Melchert-Dinkel, who is scheduled to be arraigned on May 25 in Rice County District Court, has had his nursing license revoked. He had held it since 1991, despite a record that included repeated discipline for complaints of leaving a nursing home patient unattended, being too rough, sleeping on duty, failing to take vital signs and failing to track a patient's medications.
But Mr. Watkins said his client was basically a good person. "This is not a monster," he said.
Shortly after the police interviewed Mr. Melchert-Dinkel last year, he checked into a local emergency room, state records show, saying that he was dealing with an addiction to suicide Internet sites and feeling guilty over advice he had given to people to end their lives.