Homicides by mentally ill - Mental Illness Policy Org
Homicides by mentally ill 2016-10-10T20:05:32+00:00

1000 Homicides by mentally ill

Several different studies and calculation methods (presented below) suggest that 1,000 homicides or more a year are committed by people with untreated severe mental illness..A 2011 study suggests that state homicide rates are correlated to the state’s civil commitment laws, i.e, states that make it easier to treat people with mental illness have lower homicide rates.

 From 1988 Department of Justice study

(J. M. Dawson and P. A. Langan, Murder in Families, U.S. Department of Justice, 1994)

This was a study of 2,655 homicides in 1988 drawn from a “representative sample” of 33 of the largest counties in the United States. The information was obtained from the files of prosecutors who examined the cases. They reported that 4.3 percent of the assailants had a “history of mental illness.”

In 1988 there were reported to be 20,680 cases of “murder and non-negligent manslaughter” in the United States (Sourcebook of Criminal Justice Statistics online). If the Dawson and Langan study is correct, there would have been 889 homicides (20,680 x 4.3%) caused by mentally ill individuals in the United States in 1988. Since 1988, the murder rate has decreased in the United States (16,910 in 1998). Most of the decrease is thought to be caused by (a) increased incarceration rates of career criminals; (b) fewer drug-related homicides, because of increased organization of the cocaine distribution; and (c) demographic factors, especially an aging population. None of these would be likely to significantly affect the number of homicides committed by individuals with mental illnesses. On the other hand, since 1988, public psychiatric services for individuals with mental illnesses have continued to deteriorate, and there are now many more such individuals who have been released from state psychiatric hospitals and who are not being treated.

Assuming that there had been no change between 1988 and 1998 in the percentage of homicides committed by individuals with “a history of mental illness,” then in 1998 4.3 percent of 16,910 homicides, or 727 homicides, would have been committed by such individuals.

1992 estimate based on published stories in the Washington Post

(E. F. Torrey, Violent behavior by individuals with serious mental illness, Hospital and Community Psychiatry 45:653–662, 1994)

This study of all homicides committed by severely mentally ill individuals reported by a single newspaper (The Washington Post) for the year 1992 found 13 such homicides. It was assumed that this newspaper was covering stories for the metropolitan Washington, D.C., area of approximately 3 million people. The total population of the United States in 1992 was 255 million, or 85 times that of the Washington area. Since homicides by severely mentally ill individuals were being anecdotally reported throughout the United States, in rural areas as well as in urban areas, it was assumed that the Washington metropolitan area was representative of the entire United States. The total number of homicides committed by severely mentally ill individuals in the United States in 1992 would therefore have been 1,105 (13 x 85). This, of course, includes only those cases reported by the newspaper. Between 1992 and 1998, the population of the United Sates increased from 255 million to 270 million. If the 1992 estimate was accurate, then in 1998 there would have been 1,170 homicides committed by individuals with severe mental illnesses in the United States.

1992 data from the National Comorbidity Survey published by the National Institute of Mental Health

(H. Harwood, A. Ameen, G. Denmead et al., The Economic Costs of Mental Illness, 1992, Rockville, Md.: NIMH, 2000)

Using National Comorbidity Survey data, this report concluded that, for individuals with severe and persistent mental illness (SPMI), “the SPMI population without substance-related disorders may be responsible for no more than about 3 percent of violent crime, with 3 to 5 times as much violence accounted for by the dually diagnosed (SPMI and substance disorders) population” (section on crime, p. 1.5). The study also assumed that the percentages for homicides were the same as for “violent crime” (section on crime-related costs, p. 6.8). Thus, SPMI individuals with no substance abuse disorders were said to be responsible for no more than 3 percent of homicides, but individuals with SPMI and alcohol or drug abuse were responsible for between 9 and 15 percent of homicides.

Based on the 1998 number of 16,910 total homicides, SPMI individuals (with concurrent substance abuse) would have been responsible for between 1,522 (9%) and 2,537 (15%) of them.


Given the only three studies done on this question to date, it seems reasonable to conservatively estimate that individuals with severe mental illnesses are responsible for approximately 1,000 homicides per year in the United States. No studies exist to ascertain whether this number has decreased or increased since the 1988–1992 period when these studies were done. Anecdotal data suggest that the number has increased and is continuing to increase.

Second Paper

New Study Suggests that Severely Mentally Ill Individuals Who Are Not Being Treated Are Responsible for 10 Percent of U.S. Homicides

Treatment Advocacy Center

In the first large study carried out in the United States, it has been reported that 10 percent of all homicides are committed by individuals with schizophrenia, bipolar disorder, and other psychotic illnesses, most of whom were not being treated. The study was carried out by Jason Matejkowski, Sara Cullen, and Phyllis Solomon, social workers in the School of Policy and Practice at the University of Pennsylvania. It was published in a recent issue of the Journal of the American Academy of Psychiatry and the Law.

The authors identified everyone in the Indiana state prison system who had been convicted of homicide between 1990 and 2002, a total of 1,397 individuals. The records of a random sample of 723 of these were examined, of which 518 had sufficient information to ascertain whether or not they had received a psychiatric diagnosis. Among the 518 individuals convicted of homicide, 53, or 10.2 percent, had been diagnosed with schizophrenia (n=27), other psychotic disorders not associated with drug abuse (n=14), or bipolar disorder (n=12). An additional 42 individuals had been diagnosed with mania or major depressive disorder, for a total of 95 individuals out of the 518 studied, or 18.3 percent, having a psychiatric diagnosis.

It should be noted that the study included only those individuals who committed homicides and were sentenced to prison; it did not include individuals with severe psychiatric disorders who were found to be incompetent to stand trial or not guilty by reason of inanity and therefore committed to a psychiatric facility instead of prison. The estimate of 10 percent of homicides being associated with individuals with severe, mostly psychotic, psychiatric disorders is thus a conservative estimate.

Among the 95 individuals, 77 percent were males and 71 percent were ethnically white. The victims of the homicides, for cases in which data were available, were family members or an intimate partner 57 percent of the time; friends and acquaintances, 33 percent; and strangers, 10 percent. Consistent with other studies of homicides, approximately two-thirds of the perpetrators also had concurrent problems with alcohol and/or drug abuse in addition to their psychiatric diagnoses.

An important finding of the study was that 80 percent of the mentally ill individuals who committed homicides had received past psychiatric treatment for their illness. However, according to the information available, the authors noted that “many of the offenders were not receiving treatment, a factor commonly associated with violence for adults with severe and persistent mental illness.” In addition, the authors noted that “despite their criminal histories, most offenders were not on parole or probation at the time of their offense.”

Since the 1960s, when mentally ill individuals started being released from state mental hospitals in large numbers in what has been called deinstitutionalization, there have been only two small studies in the United States of how many homicides are committed by severely mentally ill individuals. A study of Albany County, New York, reported that, among all 28 homicides committed between 1970 and 1975, 8 individuals (29 percent) were found “not guilty by reason of insanity.”, All were diagnosed with schizophrenia, and most were not being treated at the time of the crime, leading the authors to conclude that “closer follow-ups of psychotic patients, especially schizophrenics, could do a lot to improve the welfare of the patient and community.” A similar small study in Contra Costa County, California, reported that, among 71 convicted homicide offenders between 1978 and 1980, 7 (10 percent) had a diagnosis of schizophrenia, and another one had a diagnosis of drug-induced psychosis. All had been psychiatrically evaluated prior to their crimes; all had refused medications; and according to the author, “in three of the seven schizophrenics there were strong prior apprehensions about dangerousness.”

In countries other than the United States, fourteen studies have been carried out on this question. Together, these studies reported that an average of 9.3 percent (range 5.3 to 17.9 percent) of homicides were committed by individuals with severe psychiatric disorders (schizophrenia, bipolar disorder, delusional disorder, and major depression with psychosis).

It is instructive to compare the number of homicides committed by mentally ill individuals prior to the beginning of deinstitutionalization with the number in recent years. At least five studies were carried out in the United States between 1900 and 1950, during which time most people with severe psychiatric disorders were confined to state mental hospitals. The percentage of homicide offenders found to be “insane” or “psychotic” in these studies ranged from 1.7 percent to 3.6 percent. In reviewing these studies, criminologist Marvin Wolfgang concluded that “if the universe from which the insane proportion is taken refers to all those arrested for criminal homicide, the proportion [of those who are severely mentally ill] is usually 2 percent or less.”

Assuming that individuals with severe psychiatric disorders who are not being treated are responsible for 10 percent of U.S. homicides, what does this mean in terms of numbers? In 2006 there were 17,034 recorded homicides in the United States; individuals with severe mental illnesses would have therefore been responsible for approximately 1,700 of them. Over the past twenty years, during which time the deinstitutionalization of patients from state mental hospitals has been aggressively pursued, there have been a total of 388,311 homicides in the United States, with individuals with severe mental illnesses thus responsible for approximately 38,000 of them.

In commenting on the recent study, TAC founder and board member E. Fuller Torrey, M.D., commented: “These numbers are alarming, especially when it is realized that most of these homicides could have been prevented if adequate treatment had been implemented. The public thinks that most homicides are associated with substance abuse. They don’t realize that 10 percent of homicides are due to untreated severe psychiatric disorders and would not have happened if we had had an adequate psychiatric treatment system. Or failure to provide adequate treatment is producing many unnecessary tragedies. The answer is not to put these individuals back into the hospital but rather to make sure they receive the needed treatment in the community.”Homicides and Mental Illness

Homicides and Mental Illness

July 2011 American Journal of Psychiatry

To the Editor:

Dr. Matejkowski et al. are correct that he and his coauthors did not claim in their study that individuals with severe and untreated psychiatric disorders “are responsible for approximately 10% of the homicides in the United States.” That was my conclusion based on their data and on two previous studies. Among 518 offenders convicted of murder in Indiana, Matejkowski et al. said that 27 had schizophrenia, 14 had mania or bipolar disorder, 14 had another psychiatric disorder, and 58 had major depression (1). The authors themselves claimed that 95 of them, or 19%, had “severe mental illness.” Among those for whom a treatment history was known, 43% had never been treated or had been treated only once.

Such findings are consistent with a California study by Wilcox (2), who reported that seven of 71 individuals (10%) who committed homicides were diagnosed with schizophrenia, and almost all were untreated at the time of the crime. The findings are also consistent with a New York study by Grunberg et al. (3, 4) that reported that eight of 48 individuals (17%) who committed homicides were diagnosed with schizophrenia. Fourteen studies from other countries reported that indi- viduals with severe psychiatric disorders committed on aver- age 9.3% of homicides (5).

Given these studies and the absence of any contradictory data, I stand by my original claim that individuals with severe and untreated psychiatric disorders “are responsible for approximately 10% of the homicides in the United States.” Despite the importance of this issue, neither the National Institute of Mental Health nor the Substance Abuse and Mental Health Services Administration has funded a study to obtain more definitive U.S. data on this issue.

1. Matejkowski JC, Cullen SW, Solomon PL: Characteristics of per- sons with severe mental illness who have been incarcerated for murder. J Am Acad Psychiatry Law 2008; 36:74–86
2. Wilcox DE: The relationship of mental illness to homicide. Am J Forensic Psychiatry 1985; 6:3–15
3. Grunberg F, Klinger BI, Grumet B: Homicide and deinstitution- alization of the mentally ill. Am J Psychiatry 1977; 134:685–687 4. Grunberg F, Klinger BI, Grumet BR: Homicide and community-
based psychiatry. J Nerv Ment Dis 1978; 166:868–874 5. Torrey EF: The Insanity Offense: How America’s Failure to Treat the Seriously Mentally Ill Endangers Its Citizens. New York, WW Norton, 2008, pp 145, 213–218
Bethesda, Md