As an emergency services police officer in New York City for 17 years, James Gunther was one of those steely, go-to guys, a natural in a crisis.

Gunther, 45, had pulled people out of fiery car crashes, delivered babies in backseats and chased suspects down the streets of Queens. But when his second marriage began to break up a couple of years ago, it was more than he could handle.

He went to see a psychiatrist, who prescribed pills to make him feel better, but twice Gunther used them to try to kill himself. He missed child-support payments. He violated a judge's order to stay away from his wife. Three times the cop from Centereach was arrested and locked up in Nassau County jail. The last time, with pills he filched from another inmate, he tried to commit suicide yet again.

"He couldn't stand to be away from his kids," his daughter, Katherine Gunther, 19, recalled, "and he said if he didn't get out of there soon, he was going to kill himself."

After Gunther recovered, he was put in the jail's mental health tier, where a correction officer checked on him every 15 minutes. In the unseen moments between rounds, shortly after midnight on Sept. 15, 2000, James Gunther wrapped a bed sheet around his neck, looped it over a wall hook and hanged himself, finally succeeding in ending his life.

When the state ordered jail officials to explain how, despite Gunther's clear and recent history of suicidal behavior, he had not been put under constant observation, they admitted: "This was an error."

Over the past four years, errors like this one have been all too frequent on Long Island. Of the 11 inmates who have killed themselves here since 1998, including three in the past nine months, seven had diagnosed mental illnesses or showed signs of mental illness. Two others suffered from depression and one had made previous suicide threats, family members said.