BRIEF REPORT

Criminal Records of Homicide Offenders
Philip J. Cook, PhD
Jens Ludwig, PhD
Anthony A. Braga, PhD

H

OMICIDE IS A SERIOUS PUBLIC

health problem in the United
States, with 17 638 victims in
2002.1 Programs to prevent
homicide can be distinguished by
whether they are addressed to the general public or are targeted toward individuals who are considered high risk
because of their previous criminal involvement. For example, federal gun
laws incorporate both approaches; there
are general provisions, such as the near
prohibition on the private possession
of fully automatic weapons, and targeted provisions, such as the ban on
possession of any firearm by convicted felons and domestic violence offenders. Similarly, the criminal law
poses a general threat of punishment
to any adult contemplating criminal violence but targets individuals with convictions for more severe sentences.
Other criminal justice interventions are
highly targeted, affecting only individuals who are actually arrested or convicted: mandated drug programs and
other rehabilitation-oriented programs, incarceration, parole and probation supervision, and so forth.
Although the criminology literature
includes a number of studies of the
criminal histories of select groups of
homicide offenders,2-7 previous studies have typically dealt with special subsets of homicide offenders, provided few
specifics on criminal record, and lacked
comparable information for the gen-

For editorial comment see p 623.

Context Homicide prevention strategies can be either targeted toward high-risk groups
or addressed to the population at large. One high-risk group of particular interest is
adults with a criminal record. But the prevalence of a criminal record among homicide
offenders has not been reliably quantified, nor has the prevalence of criminal record
in the general population.
Objective To determine what portion of the homicide problem would be addressed
by interventions linked to arrest or conviction.
Design, Setting, and Participants A case-control analysis was performed using
a comprehensive data set of all arrests and felony convictions in Illinois for 19902001. Cases were defined as Illinois residents aged 18 to 64 years who were arrested
for homicide in 2001. Controls were all other Illinois residents aged 18 to 64 years in
2001. Illinois criminal and juvenile record information for cases and controls was compiled for 1990-2000. Five definitions of previous record were considered (arrest, arrest for a violent crime, 5 or more arrests with at least 1 for a violent crime, felony
conviction, and violent-felony conviction), each measured for 1990-2000 and for 19962000.
Main Outcome Measure The population-attributable risk: the portion of homicide offenses that would be eliminated by a hypothetical intervention that reduced
the offending risk of individuals with a record to the offending risk of those who lack
a record.
Results For 1990-2000, 42.6% of 884 cases had at least 1 felony conviction compared with 3.9% of nearly 7.9 million controls, for a population-attributable risk of
40.3% (95% CI, 37.0%-43.8%); among cases, 71.6% had experienced any arrest
from 1990-2000 compared with 18.2% of controls, for a population-attributable risk
of 65.3% (95% CI, 61.6%-68.8%). For 1996-2000, the population-attributable risk
among individuals with a felony conviction or any arrest was 31.0% (95% CI, 27.9%34.2%) and 58.5% (95% CI, 54.9%-62.1%), respectively.
Conclusions Interventions after arrest or conviction, such as supervised release, imprisonment, correctional programs, or bans on firearm possession, are targeted toward a group that has relatively high incidence of lethal violence, but they leave a
large portion of the problem untouched.
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JAMA. 2005;294:598-601

eral population. As a result, this literature offers little guidance on the relative scope of targeted vs general
prevention strategies in addressing the
homicide problem. Specifically, how
much would the homicide rate be
reduced by a hypothetical intervention that eliminated the excess risk of
homicide offending among people with
a criminal record, defined, for example,
by felony conviction within the previous decade? To answer this question,

598 JAMA, August 3, 2005—Vol 294, No. 5 (Reprinted)

we conducted a case-control study comparing the prevalence of criminal histories among homicide offenders to the
prevalence of criminal histories among
the general population.
Author Affiliations: Department of Public Policy Studies, Duke University, Durham, NC (Dr Cook); Georgetown University, Washington, DC (Dr Ludwig); and
the John F. Kennedy School of Government, Harvard
University, Cambridge, Mass (Dr Braga).
Corresponding Author: Philip J. Cook, PhD, Sanford
Institute of Public Policy, Duke University, Durham,
NC 27708-0245 (pcook@duke.edu).

©2005 American Medical Association. All rights reserved.

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HOMICIDE AND CRIMINAL RECORD

METHODS
The data include all arrests of juveniles and adults in Illinois from 19902001. They were extracted from the Illinois State Police mainframe computer
by a special program written by the Illinois Criminal Justice Information Authority and are stored at the Chapin Hall
Center for Children, University of Chicago. The specific data files used in our
analysis are described in more detail
elsewhere.8
Every “arrest event” included in these
data files was assigned a unique identification number. Every arrestee was also
assigned a unique identification number by the Illinois State Police that was
the basis for compiling an individual’s
complete arrest and conviction record
over time. (The identity of arrestees is
routinely confirmed by the police by use
of fingerprint data.) Details on the arrest event included information on the
date of arrest and the criminal charges
initially filed against the arrestee. A separate data file compiled from reports from
the state’s prosecuting attorney’s offices lists additions or deletions to the
criminal charges filed against arrestees
for each arrest event. Another data file
reported separately by the court clerks
provided information on court hearings and dispositions and was the basis
for determining convictions.
All individuals arrested for murder
or manslaughter in Illinois in 2001 were
identified in the arrest data files for that
year and linked to their arrests and convictions in Illinois for 1990-2000. We
defined the cases as just those homicide arrestees who were Illinois residents aged 18 to 64 years. Of the 1032
individuals arrested for homicide in
2001, we excluded 32 who were outof-state residents, 110 who were
younger than 18 years, and 6 who were
older than 64 years. Arrestees younger
than 18 years were excluded because
they are too young to have a criminal
history that can be meaningfully compared with those who are older.
The data on court dispositions are
somewhat less complete than the data
on arrests. To deal with this problem
of missing data, we generated 2 sets of

Table. Attributable Risks of Homicide

Criminal record during 1990-2000
Arrest
Violent arrest
Ն5 Arrests, Ն1 violent
Felony conviction
Violent-felony conviction
Criminal record during 1996-2000
Arrest
Violent arrest
Ն5 Arrests, Ն1 violent
Felony conviction
Violent-felony conviction

No. of
Cases
(n = 884)

Proportion
of
Population

Proportion
of Cases

PopulationAttributable Risk
(95% CI)

633
327

0.182
0.078

0.716
0.370

0.653 (0.616-0.688)
0.317 (0.283-0.352)

258
377
82

0.028
0.039
0.009

0.292
0.426
0.093

0.272 (0.242-0.304)
0.403 (0.370-0.438)
0.085 (0.067-0.106)

559
228
157
287

0.113
0.042
0.011
0.021

0.632
0.258
0.178
0.325

0.585 (0.549-0.621)
0.225 (0.197-0.257)
0.169 (0.144-0.195)
0.310 (0.279-0.342)

55

0.004

0.062

0.058 (0.045-0.077)

Abbreviation: CI, confidence interval.

estimates of the prevalence of felony
convictions (and convictions for violent felonies) that bracket the true
prevalence; the low estimate assumed
no conviction in cases in which the data
were unclear, and the high estimate assumed a conviction in these cases. Disposition was unclear in this sense in
56 046 instances, 22.6% of the known
felony convictions. For the sake of brevity, and because in practice it made little
difference in the pattern of results, we
report only the high estimates.
We computed the prevalence of an
arrest record for the controls (the Illinois resident population aged 18 to 64
years in 2001 who were not arrested for
homicide in that year) by counting all
individuals who were arrested at least
once in Illinois from 1990-2000 and
who were between 18 and 64 years on
April 15, 2001, and dividing by the state
population in this age range. We also
computed the prevalence of arrest from
1996-2000. Similarly, we computed the
prevalence of other types of criminal
record for 1990-2000 and 1996-2000:
arrest for a violent crime (including homicide, rape, robbery, and assault); 5
or more arrests, including a violent
crime arrest; felony conviction; and
felony conviction for a violent crime.
The Illinois population for 2001 for
residents aged 18 to 64 years was estimated from 2 sources. The noninstitutionalized population was estimated
from the US Census Bureau’s Ameri-

©2005 American Medical Association. All rights reserved.

can Community Survey for 2001.9 The
institutionalized population is not included in the American Community
Survey. We estimated it from the Census Bureau’s public use microfile data
for 200010 on the assumption that the
institutionalized population did not
change in size or composition between 2000 and 2001.
The prevalence of a record among
cases (homicide arrestees) and controls (the population at large) were compared, and attributable risks were computed.11 (The population-attributable
risk is the proportion of homicides that
would be eliminated if the homicide risk
of those with a record dropped to the
rate of those without a record.) We used
SAS software, version 9.1 (SAS Institute Inc, Cary, NC).
RESULTS
There were 884 cases and 7 879 478
controls. From 1990-2000, 42.6% of
cases and 3.9% of controls had at least
1 felony conviction, implying a population-attributable risk of 40.3% (95%
CI, 37.0%-43.8%) (TABLE). For every
definition of record, the populationattributable risk is less when record is
defined on the 5-year interval 19962000 than on the 11-year interval 19902000. It differs widely across the 5 definitions of record, depending mostly on
the prevalence of that record among
cases. For example, for records defined on the interval 1996-2000, the

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599

HOMICIDE AND CRIMINAL RECORD

population-attributable risk is 58.5% for
arrest (95% CI, 54.9%-62.1%), 31.0%
for felony conviction (95% CI, 27.9%34.2%), and 5.8% for violent-felony
conviction (95% CI, 4.5%-7.7%).
COMMENT
These estimates of populationattributable risk are useful in assessing conflicting perspectives in the literature about the importance of general
as opposed to targeted prevention strategies for homicide.
Some observers have characterized
most homicide offenders as ordinary
citizens who kill in a moment of rage
or sudden impulse when provoked by
acquaintances or relatives.12-15 This perspective seems to be supported by Federal Bureau of Investigation data indicating that about half of all homicides
are committed by an acquaintance or
relative of the victim, more than a quarter of all female victims are killed by
boyfriends or husbands, and arguments precipitate about a third of all homicides.16 This type of evidence has
been offered in support of increased
controls on firearms commerce, possession, and use in the general population to forestall lethal attacks by generally nonviolent citizens.12-15
In contrast, there is a large body of
research evidence documenting the previous criminal justice system involvement of a majority of homicide offenders.3,6,7,17-20 Most domestic homicides are
preceded by a history of assaults,20,21 and
“acquaintance” homicides often turn
out to be killings among rival gang
members, drug dealers, or organized
crime figures.22,23 This evidence supports an intervention strategy targeted toward serious offenders.
Our findings provide some support
to both perspectives. Homicide offending in Illinois is certainly concentrated among individuals with a criminal record. The prevalence of a serious
criminal record among homicide offenders is far higher than for the general population. Nonetheless, a large
part of the homicide problem lies beyond the reach of any preventive treatment that is limited to individuals who

have been arrested or convicted. For example, just 32.5% of homicide arrestees have been convicted of a felony in
the previous 5 years. An intervention
that reduced the homicide risk of felons to that of the general population
would reduce the homicide rate by just
31.0%. Such findings indicate the potential importance of general prevention strategies. Of course, whether any
prevention program is worthwhile depends on its effectiveness in influencing behavior of the target population
and on its cost.
There are several limitations to our
study, stemming from the nature of the
data. First, the identification of homicide offending with homicide arrest leads
to 2 types of misclassification. An unknown fraction of homicide arrestees in
Illinois in 2001 was not factually guilty,
and hence some individuals are incorrectly classified as “cases.” And some
proportion of killers in 2001 were not
arrested for homicide in that year so that
a relatively small number of “controls”
are in fact killers. Some indication of the
magnitude of the latter problem is given
by the fact that 60.2% of Midwestregion homicides were cleared by arrest in 2001.24 For our purposes, the
main concern is that individuals who
were arrested in 2001 were not strictly
representative of the population of killers with respect to record.
Second, we have no information on
arrests or convictions occurring in other
states. That omission is not necessarily relevant to assessing the opportunities available to Illinois state agencies to prevent lethal violence through
interventions in the lives of individuals arrested or convicted. But an outof-state record may be relevant to sentencing options and to federal law
governing firearms possession. (In federal law, any conviction for domestic
violence and any conviction for a felony
bar an individual from obtaining or possessing a firearm.25)
Third, our method for estimating the
prevalence of an Illinois criminal record among Illinois residents in 2001 has
a positive bias of unknown magnitude. We tabulated the number of in-

600 JAMA, August 3, 2005—Vol 294, No. 5 (Reprinted)

dividuals who were arrested or convicted in Illinois during a specified
period and divided by the resident
population in 2001. Yet not all individuals arrested in Illinois during the
given period were living there in 2001;
there was attrition because of death and
relocation out of state. This problem
does not apply to the cases, because all
of them are identified as individuals.
Thus, homicide arrest in Illinois is
somewhat more concentrated among
individuals with an Illinois criminal record than indicated by our statistics. As
a logical matter, this bias should be
smaller for record defined for the 5-year
period (1996-2000) than for the 11year period (1990-2000).
Finally, we have limited our analysis to the record of arrests and convictions. There are other opportunities for
official intervention in the lives of dangerous people, including civil restraining orders and court-ordered hospitalization for certain kinds of mental
illness.26,27
CONCLUSION
Interventions after arrest or conviction, such as mandatory drug treatment, supervised release, imprisonment, correctional programs, or bans
on firearm possession, are targeted toward a group that has relatively high
incidence of lethal violence, but they
leave a large portion of the problem untouched. Broader prevention strategies, including general deterrence and
the regulation of markets for “criminogenic” commodities (firearms, alcohol, and drugs), may also be warranted as part of a comprehensive
strategy.
Author Contributions: Drs Cook and Ludwig had full
access to all of the data in the study and take responsibility for the integrity of the data and the accuracy
of the data analysis.
Study concept and design: Cook, Ludwig, Braga.
Acquisition of data: Ludwig.
Analysis and interpretation of data: Cook, Ludwig,
Braga.
Drafting of the manuscript: Cook, Ludwig, Braga.
Critical revision of the manuscript for important intellectual content: Cook, Ludwig, Braga.
Statistical analysis: Cook, Ludwig.
Administrative, technical, or material support: Ludwig,
Braga.
Study supervision: Ludwig.
Financial Disclosures: None reported.

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HOMICIDE AND CRIMINAL RECORD
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