The recent mass killing in Seattle committed by Ian Stawicki has generated not only grief among the victims’ families and friends, and the community, but also people’s attempts to find some explanations for the crime. Like in Maurice Clemmons’ case (He murdered four police officers in 2009), some people and the news media hastily focused their attention on Stawicki’s alleged mental health problems. I think that the tendency to associate mental illness with violence is based on two false assumptions, to be examined in the post.

The first false assumption assumed that mentally illness makes the perpetrator less responsible for the crime, because mental illness is rooted in biological defects and is beyond the control of the person. According to criminal law, however, the presence of mental disorder does not sufficiently make the person less accountable for the offense. The most commonly used criteria for insanity defense in the criminal justice system involve the “substantial capacity test,” which suggests that mental illness can relieve a defendant of criminal responsibility, only if the defendant, as a result of mental disease or defect at the time of the crime, lacked the capacity either (a) to appreciate the wrongfulness of his or her conduct or (b) to conform the conduct to the requirements of the law. In other words, a person’s mental illness and his/her crime are two separate issues. The fact that a person with mental illness commits a crime does not suggest that the mental illness, not the person, causes the crime and makes the person less responsible for the offense.

Use Stawicki’s crime as an example, he intentionally selected and murdered his first group of victims at Café Racer and carefully thought about how to get away after the crime. He then shot and killed another woman victim and drove away with her car. His mental state indicated that he not only was capable of telling right from wrong but also executed and controlled a well-planned sequence of actions. His alleged mental health issues did not casue his crime according to the criteria of the substantial capacity test.

The second false assumption involves the belief about a high and direct correlation between mental illness and violence. Certainly portraits of mentally disordered persons by the mass media often reinforce this type of belief about and the stigma attached to them.

However, empirical evidence, which shows that the correction between mental illness and violence at most is complicated, does not support the belief. MacArthur Violence Risk Assessment study, a major and comprehensive investigation with researchers from across the United States on the issue, has shed new light on the debate by examining specific risk factors for violence among psychiatric populations. The findings indicated that the mentally ill persons with the following characteristics have a risk for violent behavior (see Harris & Lurigio, 2007):

1. A co-occurring diagnosis of a substance use disorder, which was robustly predictive of violence.

2. Previous violence (based on self-report, arrest records, and hospital records), which was strongly correlated with future violence.

3. Persistent violent thoughts or daydreaming about harming others.

4. Anger or a generally “suspicious” attitude toward others.

5. Psychopathy or antisocial personality, which is related to the general propensity for violence in both psychiatric and non-psychiatric populations.

However, the following factors were not strong predictors of violence:

1. A diagnosis of schizophrenia, which was associated with a lower rate of violence than a diagnosis of a personality or adjustment disorder.

2. Delusions, the presence of which is not associated with violence.

In short, the two false beliefs both view mental illness as an expedient variable in explaining criminal behavior, using the factor to either shift the blame away from the offender or prematurely assume a person’s dangerousness or risk to others.


Harris, A., & Lurigio, A. J. (2007). Mental illness and violence: A brief review of research and assessment strategies. Aggression and Violent Behavior, 12, 542-551. doi:10.1016/j.avb.2007.02.008

About the Author

Key Sun Ph.D.

Key Sun, Ph.D., is a psychologist and social worker. He has taught at Central Washington University and Bastyr University.

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