AUBURN — A judge found a Lewiston woman who set her mattress on fire last year not criminally responsible by reason of insanity on Tuesday.

Misty Cornell, 45, was committed to Riverview Psychiatric Center in Augusta under the care of the commissioner of the Department of Health and Human Services.

Cornell will be evaluated every six months to determine her state of mind.

She was scheduled for a bench trial at Androscoggin County Superior Court, but Assistant District Attorney Andrew Matulis and defense attorney Allan Lobozzo agreed to the insanity finding and recommended it to the judge, who approved.

Lewiston’s fire investigator, Paul Ouellette, testified Tuesday that on March 29, 2013, he inspected the scene of the fire in a second-floor apartment at 75 Spring St., Lewiston. He said he found a burned mattress lying on the floor of the kitchen. He determined that the fire was intentionally set. No liquid fuel was found, he said.

According to a police report, Cornell had confessed to police shortly after the incident when she went to the Lewiston police station on Park Street.

She was suicidal and said she felt like there was a vise around her head that was squeezing her brain, Lobozzo said.

A recording of Cornell’s call to a police dispatcher was played in court. She could be heard admitted to setting the fire.

Peter Donnelly, a court-ordered psychologist, testified Tuesday that Cornell had not been taking her prescribed medication for bipolar disorder. She had been having auditory and visual hallucinations at the time of the fire. She also suffered from post-traumatic stress disorder from domestic violence in her home during her upbringing, he said.

After the fire, Cornell was taken to St. Mary’s Regional Medical Center, where she was treated for three weeks until she was stable enough to leave.

Donnelly said Cornell had nearly a dozen psychiatric admissions since 2006. He said she didn’t have a distinct recollection of setting the fire because she was “severely mentally ill at the time.”

Cornell had been charged with two felonies: Class A arson, punishable by up to 30 years in prison; and aggravated criminal mischief, a Class C crime, punishable by up to five years in prison.

Justice MaryGay Kennedy determined that Cornell was not criminally responsible by reason of insanity. Kennedy said that Cornell lacked the capacity to appreciate the wrongfulness of her conduct at the time of the fire because she had been off her medication and was in “full mania.”

A first-floor neighbor in the three-family building who lived with her husband and three children had called 911 when she saw smoke billowing out of second-floor windows at the back of the building. She ran outside when she saw smoke coming from the building’s stairwell.

Before Cornell was led from the courtroom, Kennedy said: “Miss Cornell, very good luck to you.”

cwilliams@sunjournal.com