NGRI Population Less Likely to Use Firearm Than General Offender Population

Amanda Kingston, MD, Yale School of Medicine

Amanda Kingston, MD

A new study presented at the American Psychiatric Association’s 2018 Annual Meeting in New York City, found that when compared to convictions in Connecticut, those adjudicated as mentally ill are less likely to use a firearm than the general population but more likely to use a knife.

Researchers from Yale University School of Medicine conducted a study to determine if those adjudicated as mentally ill are less likely to use a firearm in the commission of a crime than the general offender population.

Information was collected July 1970—June 2017 from the Connecticut database of 382 not guilty by reason of insanity (NGRI) acquittees which included information on the date of offense, age at offense, weapon usage, and diagnosis. Individuals found NGRI were adjudicated as mentally ill.

The control group encompassed convicted offenders in Connecticut. The incidence of firearm use in the NGRI population compared to the general population of offenders.

Study participants in the acquittee group were mainly male (85.9%). The age ranged from 16—73 years old, with a mean age of 33 years.

Findings were compared to the uniform crime rate (UCR) statistics from the state of Connecticut and concluded that when compared to convictions in Connecticut, the acquittee population was less likely to use a firearm but more likely to use a knife.

While men and women were found to mainly use knives as a weapon of choice, firearms were found to be used predominately by a younger group of males in the NGRI population. There were no women that used a rifle/shotgun, but 89% of handgun use was by men.

“Men still don’t prefer handguns, but they use them more frequently,” Amanda Kingston, MD, Yale University, said.

Among the NGRI population, the weapon of choice was a knife (26%), followed by an other/unknown weapon (arson, pepper spray, etc.) (20%) and no weapon (17%), however handguns (18%) ranked fourth, and rifles/shotguns (7.1%) sixth but when combined, remained fourth.

The UCR violent offenders, however, preferred to use no weapon (35%) in the commission of a crime. Additionally, firearm use in the NGRI was more closely related to substance use and personality disorders than psychotic or mood disorders.

Researchers broke down the most commonly used weapon by diagnosis concluding the below:

• Schizophrenia/Other Psychoses: Knife, other weapon or no weapon
• Mood Disorder: No weapon, knife or handgun
• Organic Brain Syndrome: Knife, other weapon, handgun
• Substance Use Disorder: No weapon, handgun, knife
• Personality Disorder: Other weapon, handgun, knife
• Developmental Disorder: Other weapon, knife, no weapon
• Impulse Control Disorder: Other weapon, no weapon, knife

The key takeaway, Kingston concluded, is that a small group of the population with a violent past, adjudicated as mentally ill, used firearms in the commission of a crime. While those with mental illness may be violent, if/when that occurs, a firearm is rarely used.

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