An attorney says a suburban New York man accused of strangling his mother snapped after years of caring for the ailing 88-year-old woman.

Defense attorney Paul Delle offered the insanity defense Friday in the trial of James Olson. He has pleaded not guilty to murder charges.

Prosecutors say Olson used a necktie to strangle Ruth Olson in April 2011 inside the modest Garden City, Long Island, home they had shared for decades. Olson then tried to commit suicide by slashing his neck and wrists.

When a 911 operator asked what happened, he said: "Murder, suicide. Unsuccessfully."

Nassau County prosecutor Christine Geier said Olson had planned the killing, even picking out the necktie he would use the night before.

She said Olson knew what he was doing was wrong.