He Helped a Woman End Her Own Life. Was It Manslaughter, or Mercy? He Helped a Woman End Her Own Life. Was It Manslaughter, or Mercy?

They checked into a motel room in upstate New York, with a gas canister and a plan to end her decades of physical pain.

A king room at the Super 8 motel in Kingston, N.Y., is a forlorn place. Mismatched night stands. An armchair with visible stains. Soggy grass outside the window.

“Resting for the journey ahead,” the do-not-disturb sign says. It shows a lone car on a two-lane road, sandy hills beneath fluffy white clouds in the distance.

Doreen Brodhead checked into just such a room in the fall, No. 102, the last one on the right at the end of a narrow, dimly lit hallway. With her was Stephen P. Miller, a former doctor from Arizona with a prison term in his past. They had gotten to know each other online.

Ms. Brodhead, a 59-year-old Kingston native, had lived with severe pain in her neck and back most of her adult life. She attributed it to her brief career as a dental hygienist. No one — not doctors or surgeons or chiropractors or acupuncturists — could fix it.

Mr. Miller, 85, was familiar with pain. As a toddler, he had been badly burned in a bathtub of scalding water, a relative said. Now, along with other ailments, he had a chronic spinal condition.