Doreen Dunn had lived in pain for a decade by the time she killed herself in May 2007.

After consulting with the nonprofit Final Exit Network, she used helium and a plastic bag to end her life on the couch of her Apple Valley home.

Now, an investigation of the 57-year-old's death puts Minnesota at the center of a national debate over assisted suicide.

Dakota County Attorney James Backstrom will present evidence to a grand jury this week seeking indictments against the Georgia-based Final Exit Network and a handful of its members, accusing them of breaking state laws against aiding a suicide and interfering with a body.

It's the third time in recent years that prosecutors around the nation have gone after the group, which mostly fought off high-profile criminal charges in Arizona and Georgia.

The network insists that its volunteers are within the law because they don't provide equipment or physically participate in suicides, only offering information and support, sometimes by being present during the suicide.

"We do give explanations of how to do it," said Robert Rivas, a Florida attorney for the Final Exit Network. "We don't advise anybody to do it."

Backstrom confirmed the investigation and his intentions to bring the case before a grand jury but declined to comment beyond a written statement.

"This investigation is complex, as it involves a non-Minnesota corporation," he said. "When further information becomes public ... we will share it with media outlets."

The network says it mostly operates online and over the phone, receiving requests from people around the country who want to arrange an "exit."

Painful life, quiet death

Dunn made an "exit request" in January 2007, writing in a letter that she was "living with unbearable, excruciating chronic pain that has spread throughout my whole body since 12/96."

Toward the end of the handwritten letter, signed Doreen Gunderson Dunn, she said, "Have fought the good fight for 10 yr. to try & get better but it is futile and without an exit will be left in some nursing home in unbearable pain for who knows how many years."

She also submitted a note from her doctor, released in part by the network Monday, that confirmed she was completely disabled and suffered from multiple painful conditions, some related to a 1996 medical procedure.

"She had sought every form of treatment that medical science could provide and was told that she had really no choice but to live with these conditions," Rivas said.

He said the Final Exit Network requires such documentation. Once a person is deemed to be suffering from an incurable and chronic -- but not necessarily terminal -- condition and found mentally competent, the group offers an "exit guide" and meetings with volunteers who will attend a suicide, but not assist in one, if requested.

"Nobody likes to die alone," Rivas said.

Two volunteers from the Final Exit Network traveled to Minnesota the day Dunn died. Rivas said he did not know whether they were with Dunn.

He said Dunn did not want her family, including her then-estranged husband, to be aware of her plan.

An autopsy by the Dakota County medical examiner found that Dunn died of coronary artery disease. It also noted that Dunn had suffered from chronic pain.

From Georgia to Minnesota

Dakota County's investigation began in the wake of a highly publicized and unsuccessful attempt by Georgia prosecutors to go after the network.

Rivas said the Georgia Bureau of Investigation distributed information it had discovered about the network's members to other law enforcement agencies across the country.

"Of all the hundreds of agencies that received this information, not one has bitten on the bait except Dakota County, Minnesota," Rivas said.

The Georgia criminal charges were dismissed in February after the state's supreme court struck down the state's law criminalizing assisted suicide. The network's lawyers had argued that it violated free speech rights under the First Amendment.

Rivas said he expects to make the same arguments in opposition to Minnesota's law against assisted suicide, which he said is being used to target the network as a whole and four individuals: Dr. Lawrence Egbert of Baltimore, the network's medical director in 2007; Jerry Dincin of Highland Park, Ill., an "exit guide" who worked on Dunn's case; Thomas Goodwin of Atlanta, and Punta Gorda, Fla.; and Roberta Massey of Delaware.

There's a difference in Minnesota -- a law making it a misdemeanor to tamper with a body.

Rivas said network volunteers will, if requested, remove evidence of a suicide after the death, but reiterated that he did not know what they did for Dunn.

"It's possible they followed the normal routine," he said.

Dakota County Medical Examiner Dr. Lindsey Thomas, whose office did Dunn's autopsy, declined to talk specifically about the case.

But generally, she said, had it been reported that there was a helium tank and a plastic bag at the scene of a death, she would consider suicide a possible cause.

The Final Exit Network's methods have also come under scrutiny in Arizona, when four members -- two of whom also figure in the Minnesota inquiry -- faced felony charges.

In 2011, a jury found Egbert not guilty and deadlocked in the case against another volunteer, who later pleaded guilty to a lesser charge.

"[We're] not surprised that it would pop up again somewhere else," said Frank Kavanaugh of the network's advisory board. "We have to deal with them one by one. We do feel that we stay on the right side of the law."

Minnesota's law against assisted suicide was put to use just last year when a judge found William Melchert-Dinkel, a former nurse, guilty of two counts of felony advising and encouraging suicide for coaxing two people over the Internet to kill themselves.

Katie Humphrey • 952-746-3286