Michelle Kehoe’s defense team was unable to prove she was not guilty by insanity during her weeklong trial in the Grundy County Courthouse.

The insanity defense is an unusual move and one that rarely ends successfully for the defendant, experts say.

“It isn’t used very often — juries are quite skeptical,” UI law Professor David Baldus said.

Iowa City criminal defense attorney David Pollack agreed.

“It’s a tough sell; people don’t want to be duped,” he said.

The insanity defense is used in fewer than 1 percent of criminal trials, and it is successful only a quarter of the time, according to the National Center for State Courts.

Kehoe, 36, of Coralville, was found guilty on Thursday of killing her 2-year-old son, Seth Kehoe, attempting to kill her other son, 7-year-old Sean Kehoe, and child endangerment causing injury.

After binding the children with duct tape and cutting their necks, Kehoe slit her own throat on Oct. 26 at the Hook ’N’ Liner pond near Littleton, Iowa.

Kehoe’s defense team argued that her mental state at the time of the crimes may have been deteriorated, causing her not to know the difference between right and wrong. In that case, she shouldn’t have been held accountable for her actions, they said.

A defense witness, psychiatrist Marilyn Hutchinson, pointed to Kehoe’s low score on a Global Assessment of Functioning test as a possible assertion for Kehoe’s insanity.

The Global Assessment of Functioning test is a scale from 1 to 100 — with 100 meaning good mental health — that reflects a clinician’s judgment regarding the everyday functioning ability of a patient.

The evaluation examines the patient’s diagnosed disorders, medical history, living situation, occupational problems, and legal problems.

UI psychology Professor Michael O’Hara said a person who scored around a 40 would be fairly impaired in every day activities and reality.

“[A person who scored 40] is someone who is pretty ill but not psychotically ill,” he said.

O’Hara said a patient with this score would be impaired on many levels and “nearly psychotic.”

“In the ordinary course of things, a person at that level would usually know right from wrong but not necessarily,” he said. “It gets very complicated.”

Kehoe has not yet been sentenced, but Iowa law states a person found guilty of murder must serve life in prison with no chance of parole. She will more than likely go to the Iowa Medical & Classification Center in Oakdale.

If the jury had found Kehoe insane, she most likely would have been sent to the same facility, but a judge could have eventually found her mentally competent enough for release, Baldus said.

Pollack said an insanity plea is hard for the defense to prove, and juries may be wary when listening to one.

“I don’t know that there’s a preconceived notion, but the burden is on the defense to prove it,” he said.