Research in Brief 

U.S. Department of Justice

Office of Justice Programs

National Institute of Justice

Co­Offending and Patterns of Juvenile Crime

D

E

C. 0

5

www.ojp.usdoj.gov/nij 
U.S. Department of Justice

Office of Justice Programs

810 Seventh Street N.W.

Washington, DC 20531

Alberto R. Gonzales

Attorney General

Regina B. Schofield

Assistant Attorney General

Glenn R. Schmitt

Acting Director, National Institute of Justice

This and other publications and products

of the National Institute of Justice can be

found at:

National Institute of Justice

www.ojp.usdoj.gov/nij

Office of Justice Programs

Partnerships for Safer Communities

www.ojp.usdoj.gov
DEC. 05

This report is based on

findings presented by the

authors in “Patterns of

Juvenile Delinquency and

Co­Offending,” in Crime

and Social Organization,

vol. 10 of Advances in

Criminological Theory, E.

Waring and D. Weisburd

(eds.), New Brunswick,

NJ: Transaction Publishers, 2002: 15–30; and “A

Longitudinal Examination

of the Relation between

Co­Offending With Violent Accomplices and Violent Crime,” Aggressive

Behavior 28 (2) (2002):

97–108. These articles are

available from 

the National Criminal 

Justice Reference Service

at www.ncjrs.org.

Co­Offending and Patterns of 

Juvenile Crime

Findings and conclusions of the research reported here are those of the

authors and do not necessarily reflect the official position or policies of 

the U.S. Department of Justice or the National Institutes of Health.

This research was supported by the National Institute of Justice under

grant number 92–IJ–CX–K008, “Delinquent Networks in Philadelphia: 

Co­Offending and Gangs.” The study’s final report, “Longitudinal

Examination of the Relation Between Co­Offending with Violent

Accomplices and Violent Crime,” by Kevin P. Conway and Joan McCord

(2001), is available at www.ncjrs.org/pdffiles1/nij/grants/192289.pdf. 

NCJ 210360 
RESEARCH IN BRIEF /DEC. 05

ABOUT THIS REPORT

Observers of juvenile crimes

have long noticed that most

are co­offenses; that is, they

involve more than one offender. An NIJ­sponsored study of

juvenile offenders in an urban

center uncovered several patterns of crime related to cooffending. This report focuses

on three of those patterns—

how co­offending is related

to (1) the age of offenders,

(2) recidivism, and (3) violence.

What did the

researchers find?

The distribution of co­offending

exaggerates the contribution 

of young offenders to crime

events; ignoring co­offending

when computing crime rates

may produce severely misleading reports about crime and 

the effects of incarceration.

Offenders age 13 and under

are more likely to commit

crimes in pairs and groups

than are 16­ and 17­year­old

offenders. About 40 percent

of juvenile offenders commit

most of their crimes with

others. Co­offenders also are

more likely than solo offenders to be recidivists. When

very young co­offenders

were compared with very

young solo offenders, only

the co­offenders had high

recidivism rates and only the

co­offenders committed high

numbers of violent crimes.

These young co­offenders

warrant special attention

from the criminal justice 

system.

Co­offending actually may

increase the likelihood that

offenders will commit violent

crimes. When young offenders affiliate with offenders

who have previously used

violence, the result appears

to be an increase in the likelihood that they will subsequently commit a violent

crime. Co­offending violence

rose throughout adolescence

among the study group.

These trends suggest that

an effective strategy would

be to intervene early in the

development of a criminal

trajectory and to especially

target co­offenders. For

example, police could 

inquire about co­offending

and record all participants 

in a crime.

ii
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

Joan McCord and Kevin P. Conway

Co­Offending and Patterns of

About the Authors

The late Joan McCord,

Ph.D., Professor of Criminal

Justice at Temple University,

was a groundbreaking

criminal justice researcher

and an eloquent teacher,

speaker, and writer in the

field, often focusing on

juvenile crime, violence,

and the efficacy of intervention programs. Kevin P.

Conway, Ph.D., is Deputy

Branch Chief of the Epidemiology Research

Branch at the National

Institute on Drug Abuse.

His research interests center on drug abuse etiology

and juvenile delinquency,

with emphasis on links

between antisocial behavior and drug abuse.

Juvenile Crime

Juveniles who commit

crimes typically commit them

in the company of their

peers. This basic fact has

been regularly reported in the

literature since the late

1920s.1 Nevertheless, with

rare exceptions, contemporary research focuses almost

exclusively on juvenile delinquents as individual actors.2

Indeed, police records tend

to undercount co­offending,

and published crime rates

rarely take co­offending into

account.

Most crime rates are computed from individuals, with

an assumption that each

criminal event reported by or

about an individual represents a crime event (see

“Measuring Juvenile Crime”).

Yet co­offenders provide a

basis for multiple reports of

single crime events. Not only

are those who first offended

before age 13 most likely to

be co­offenders, but also

the sizes of their offending

groups (from 2 to 30 in the

current study) tend to further

exaggerate the contributions

of youthful offenders to

crimes. This exaggeration

seems to contribute to a 

fear of youths that may be

counterproductive.

Analyses that consider both

co­offending and age at first

arrest show that youthful

offenders are most at risk

for subsequent crimes if

they commit their crimes

with accomplices. Although

very young offenders are

responsible for a high proportion of juvenile crimes,

their annual crime rate is

not particularly high unless

they are co­offenders.

Violence appears to be

learned in the company of

others. Those who commit

crimes with violent offenders,

even if the group does not

commit violent crimes, are

likely to subsequently commit violent crimes. This suggests that young offenders

pick up attitudes and values

from their companions.

To address issues raised 

by co­offending, including

whether co­offending

increases violence, the

National Institute of Justice

sponsored a study in

Philadelphia that examined

1
RESEARCH IN BRIEF / DEC. 05

MEASURING JUVENILE CRIME

Data about juvenile crime typically come from three

sources: arrest data, reports from victims, and self­reports

about crimes committed. These sources have limitations

and important intrinsic inaccuracies—one of which is that

they ignore co­offending.

Arrest data.

Reports, arrest data count each arrest of each individual

as a crime, thus relying on such factors as policies of particular police agencies, cooperation of victims, and the

skill of crime perpetrators. If more than one person is

arrested for a single crime, information from arrests

inflates the crime rate. Multiple arrests of a single person

also inflate the crime rate when rates are presented as a

proportion of the population who are arrested.

households, victims over the age of 12 report their experiences with specific crimes (rape, sexual assault, personal

from this source for homicides, victims under the age of

about perpetrators is available from these records only for

crimes involving contact between victim and criminal.

Estimates of juvenile crimes depend on the victims’ estimates of age. Crimes with more than one victim may have

multiple reports in these records.

Self­reports. Self­reports about crimes committed are coltage of the fact that schools provide a convenient location

for data collection, but they typically miss the most likely

perpetrators of crimes—those absent from school

reporting questionnaires record delinquencies that would

not be considered serious enough to call police, and few

obtain information about the more serious types of crimes

included on the FBI Indexes. Self­reports of crimes tend to

Typically derived from the FBI’s Uniform Crime

Victims’ reports. Victims’ reports have been systematically

collected since 1973 in the National Crime Victimization

Survey. Using a nationally representative sample of

robbery, aggravated and simple assault, household burglary, theft, and motor vehicle theft). Data are not available

13, or victims who are not parts of households. Information

lected in a variety of settings. Many surveys take advanbecause of illness, dropping out, or truancy. Many selfreflect social responses to criminality, with accuracy of

reporting varying by gender, ethnicity, and recidivism.

the criminal histories of a

random sample of juvenile

offenders. This Research in

Brief discusses the study’s

findings and implications,

considering four questions:

❋ Why consider co­offending?

❋ How is co­offending related

to the age of offenders?

❋ How is co­offending related

to recidivism?

❋ How is co­offending related

to violence?

Why consider 

co­offending?

Co­offending distorts reported crime rates by equating

number of offenders with

number of incidents and may

increase a juvenile’s risk for

committing violent crimes

through association with violent peers. Statistics on

crimes typically are based on

the number of criminals

accused or convicted of

crimes. Even when selfreports are used, they indicate only which individuals

within a stipulated population

have committed crimes. Such

statistics create a distorted

picture of crime because

many crimes are committed

by more than one criminal

2
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

and the proportion differs

among different groups.

The distortion can be seen in

the rare instances when

crimes by lone offenders

have been separated from

those committed by multiple

offenders. For example, the

Sourcebook of Criminal Justice Statistics, 2001, reports

that 64 percent of the violent

crimes attributed to lone

offenders were committed 

by white offenders, but only

51 percent of the violent

crimes attributed to multiple

offenders were committed 

by offenders in “all white”

groups.3 These figures suggest that nonwhites are more

likely to offend in groups.

Therefore, crime rates based

on arrests may exaggerate

the contributions of nonwhites to crime in the United

States.

The distortion has a particularly strong effect for juvenile

crimes. In 1997, for example,

the Supplemental Homicide

Reports indicated that 44 percent of murders known to

involve juveniles involved

more than one perpetrator.4

According to the Bureau of

Justice Statistics, 23 percent

of violent crimes in 1999

attributed to lone offenders

were committed by juveniles

under the age of 18, whereas

over 40 percent of violent

crimes attributed to multiple

offenders were committed by

juveniles.5

The fact that particular crimes

are committed by more than

one criminal not only distorts

the connection between

criminals and crimes, but also

distorts estimates of effects

from various crime prevention policies. For example,

researchers questioning the

focus on incapacitation of

high­rate offenders noted that

offenders’ crime rates would

be exaggerated if they had

committed a large proportion

of their crimes in groups. To

more accurately measure the

effect of incapacitation on

crime rates, attention also

must be given to the continued criminal involvement of

the co­offenders who remain

in the community.6

In addition to distorting crime

rates based on individuals

and distorting the effects 

of intervention policies, cooffending may actually

increase participation in

crimes.7 Furthermore, the

present study provides evidence that co­offending may

increase violence (see “How

co­offending is related to 

violence,”page 8).

The fact that

particular

crimes are

committed by

more than one

criminal not

only distorts 

the connection

between

criminals and

crimes, but 

also distorts

estimates of

effects from

various crime

prevention

policies.

3
RESEARCH IN BRIEF / DEC. 05

How co­offending 

is related to the age 

of offenders

Because prior evidence8 suggests that youths who start

offending early commit more

crimes than those who start

late, effects of the age of first

criminality should be considered along with co­offending.

Most offenders in the Philadelphia study committed

their first offense between

the ages of 13 and 15.

Researchers identified youths

who committed a crime

before the age of 13 as

“young starters” and those

who committed a first crime

after age 15 as “late starters.”

They noted a relative decline

in co­offending in relation to

age, but this reflects a sharp

increase in the number of

crimes committed by single

offenders rather than a

decline in the number of 

co­offenses (see exhibit 1).

0 2 3 4 5 6 17

Number of crimes

Offender age

0

50

00

50

200

250

offender

2 offenders

3 offenders

Exhibit 1. Number of crimes by number of offenders and age

4
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

From ages 10 to 17, crimes

committed alone, in pairs,

and in groups increased. The

number of crimes committed

alone increased more rapidly

than the number of crimes

committed with accomplices.

Rates for pairs and for groups

were almost identical after

age 14.

When researchers differentiated property crimes from

violent crimes,9 they found a

decline in co­offending after

the age of 15 for property

offenses (see exhibit 2). This

decline, however, was paralleled by a rise in solo property offending. Co­offending

violence increased throughout adolescence, while solo

violent offending leveled off

around age 15. Among 16­

and 17­year­old offenders, 

violent crimes were almost

twice as likely to be cooffenses as solo offenses.

Exhibit 2. Crimes, age, and co­offending

0 2 3 4 5 6 17

Number of crimes

Offender age

0

20

40

60

80

00

20

Solo violent

Co-violent

Solo property

Co-property

5
RESEARCH IN BRIEF / DEC. 05

The youngest offenders at

first arrest were the most

likely to mix co­offending and

solo offending, but least likely

to commit all their crimes

alone. Those first arrested at

ages 16 or 17, on the other

hand, were most likely to

commit crimes alone. About

40 percent of offenders committed most of their crimes

with accomplices, regardless

of their age at first arrest (see

exhibit 3).

Exhibit 3. Age at first arrest and co­offending

How co­offending is

related to recidivism

The Philadelphia delinquents

first arrested when they were

under 13 years of age had

higher rates of recidivism

than those first arrested

when they were older. Cooffending, however, distorts

the picture of recidivism

because there are actually

fewer crime incidents than

individual crime rates indicate

ercent of crimes committed with co-offenders

M tly solo (0–24%)

– 4% co-offending

M tly co-offendin (75–1 0%)

10

20

30

40

50

60

A 12 and younger Ages 13–15 A 16–17

A at first arrest Age at first arrest Ag irst arrest

ercent

6
CO­OFFENDING AND P A TTERNS OF JUVENILE CRIME

(see exhibit 4). Specifically,

crime rates are inflated if cooffending is not taken into

account. In contrast, crime

rates that account for cooffenders count each crime

incident once even if multiple

offenders have been arrested

for the crime. The crimeincident ratio, which accounts

for co­offending, is greatest

for the young starters—

indicating that crime rates 

for young delinquents are

most likely to be inflated

when co­offending is not

taken into account.

Study findings on recidivism

provide a good example of

the increased information

that comes from recognizing

co­offending. The number of

Index crimes was consistently higher for delinquents who

co­offended at least 25 percent of the time. This pattern

was particularly evident for

the young starters. The young

starters who co­offended at

least 25 percent of the time

were arrested for almost

twice as many Index crimes

as the young starters who

typically committed solo

offenses.10 Thus, the number

who mostly co­offend committed the most crimes.

An examination of annual

crime rates further demonstrates how crime rates can

be inflated by inattention to

co­offending. In each category

of age for first arrest, individual co­offending rates were

higher than solo rates (see

exhibit 6). The offenders first

age is a result of smaller groups committing crimes, of

reform, or of shifts from co­offending to solo offending,

researchers in a 1991 study* analyzed criminal records of

viduals with long criminal histories tended to move from

group to solo offending. Both recidivism and co­offending

declined with increasing age at first offense. The same

study also reported that co­offending delinquents committed crimes at higher rates than solo offenders.

Offending: Results From [a] Prospective Longitudinal Survey of London

Males,” Journal of Criminal Law and Criminology  82 (1991): 360–395.

To determine whether a decline in group offending with

411 male criminals in London. They discovered that indi­

*See Reiss, A.J., Jr., and D.P. Farrington, “Advancing Knowledge About CoExhibit 4. Crime incidents and co­offenders

Mean number of

Age at  Reported Actual Crime­incident 

first crime crimes incidents* ratio

< 13 years 7 3 2.3

of arrests for Index crimes 13–15 years 4 2 2.0

reflected both the age at first 16–17 years 2 1 2.0 arrest and the proportion of

crimes that were co­offenses

(see exhibit 5), revealing that *When co­offending is factored in.

young­starter delinquents

7
RESEARCH IN BRIEF / DEC. 05

arrested at ages 16 and 17

had the highest rates for both

solo and co­offenses. However, these high recidivism

rates are due to both the

compressed duration of their

measured criminal activities

and the fact that such a high

proportion of their crimes are

co­offenses.

Despite committing crimes

at lower rates, the offenders who had first been

arrested under the age of

13 had the highest ratio of

co­offending to solo offending. But young starters are

Exhibit 5. Age at first crime, 

co­offending, and Index crimes 

Age at first crime Mean number 

and rate of  of Index

co­offending crimes

not high recidivists if one

considers the length of time

they are exposed to the 

juvenile justice system.11

These analyses show not only

that crime rates based on individuals are most inflated for

young­starting delinquents,

but also that targeting youthful co­offenders could be the

most productive approach to

reducing future crime.

How co­offending is

related to violence

Those who generally committed crimes with others were

more likely to commit violent

crimes than were solo

offenders. The association

between co­offending and

violence was strongest for

young starters.

< 13 years Young starters. On average,

Co­offend < 25% of crimes 3 offenders who had accomCo­offend 25–74% of crimes

Co­offend > 74% of crimes

6

6 plices for at least 25 percent

of their crimes and had been

13–15 years arrested before the age of 13

Co­offend < 25% of crimes 2 committed more than two

Co­offend 25–74% of crimes

Co­offend > 74% of crimes

4

3 violent crimes (see exhibit 7).

16–17 years Young starters who commitCo­offend < 25% of crimes 1

Co­offend 25–74% of crimes 2

Co­offend > 74% of crimes 1

Note: Figures have been rounded.

ted most of their crimes

alone, however, were not particularly prone to committing

violent crimes. On the other

hand, co­offending young

starters were considerably

more likely to commit violent

8
CO­OFFENDING AND P A TTERNS OF JUVENILE CRIME

crimes than were late starters, especially late starters

who mostly worked solo.

Thus, because the vast

majority of young starters

commit many of their crimes

with others, the effects of

age and co­offending on violence tend to be confounded.

Is violence learned? The

association between cooffending and violence raises

the question of whether kids

who tend to be violent hang

out together and therefore

commit violent crimes or

Among the 236 offenders

who had not been violent

before their first co­offense,

90 participated in a violent

first co­offense; among

these, 62 percent committed

at least one additional violent

Exhibit 6. Individual crime rates and co­offending

Individual annual crime rates

Age at Ratio of co­offending 

first arrest Solo crimes Co­offenses to solo offending

< 13 years 0.3 0.6 1.9

13–15 years 0.4 0.6 1.5

whether learning accounts

for some of the high level of

violence. To test the latter,

researchers identified 236

offenders in the random

sample of 400 who had not

committed violent crimes

before committing a crime

with others.

16–17 years 0.6 0.7 1.2

Exhibit 7. Young co­offenders—at risk for violence

Age at first crime and 

rate of co­offending Mean number of violent crimes

These offenders committed < 13 years

their first co­offenses with Co­offend < 25% of crimes 1.0

514 accomplices. Groups Co­offend 25–74% of crimes 2.4

2.0 ranged from 2 to 15 offend­ Co­offend > 74% of crimes

ers. Pairs committed 42  13–15 years

percent of these crimes. Co1.7

Co­offend < 25% of crimes 0.9

offenders typically matched Co­offend 25–74% of crimes 1.1

their accomplices in ethnic Co­offend > 74% of crimes

identity.12 Age comparisons 16–17 years

revealed that most of the Co­offend < 25% of crimes 0.3

offenders identified in their Co­offend 25–74% of crimes 0.8

0.8 first co­offense were younger Co­offend > 74% of crimes

than their accomplices.13

9
RESEARCH IN BRIEF / DEC. 05

offense after this first one.

Another 61 juveniles participated in a nonviolent cooffense with co­offenders

who had previously been 

violent. These juveniles were

even more likely to subsequently commit a violent

crime than those who had

actually participated in a 

violent crime for their first 

co­offense.14

Exhibit 8. Violent crimes after first co­offense 

(percent of category)

Percent arrested 

for a violent crime

No violent accomplices

0

20

40

60

80

00

< 3 13–15 6–17

Age at first arrest

Violent accomplices

To check whether peer contagion15 may have influenced

the learning of violence,

researchers divided the previously nonviolent offenders

who committed a first cooffense that was not violent

into two groups according to

whether their accomplices

had been violent before the

target co­offense. Those who

committed a nonviolent

offense with violent people

were considerably more likely

to commit a subsequent violent crime—80 percent of

those with violent accomplices, compared with 56 

percent of those with only

nonviolent accomplices, committed at least one violent

crime after the co­offense.16

The data showed no systematic relationship between age

at first offense and whether

or not nonviolent offenders

co­offended with violent

offenders for a first cooffense. Nevertheless, both

whether a violent offender

participated in the first cooffense and age at first arrest

predicted whether a previously nonviolent offender

would commit a violent crime

(see exhibit 8).

Committing a first co­offense

with violent accomplices

10
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

contributed to the likelihood

that violent crimes would be

committed, regardless of age

at first arrest. That is, violent

peers increase the likelihood

that nonviolent offenders will

commit violent offenses.

How may violence be

learned? Peer delinquency

seems to be more than 

a training process for learning how to be delinquent.

Interaction among delinquent peers apparently

encourages and escalates

their proclivity to commit

crimes. Co­offenders may

learn through the influence

of violent accomplices that

violence can be an effective

means for getting money or

satisfying other desires. 

They also may learn that

insults or fear provide adequate grounds for violence.17

An adequate theory of crime

should take into account

both how others influence

individual behavior and how

individuals selectively seek

companions who are likely to

promote criminal behavior.

Construct Theory postulates

that co­offending provides a

young offender justification

for continued delinquency,

encouraging him or her to

seek out accomplices and

commit additional crimes

(see “Construct Theory”).

This implies that interventions need not be directed at

deep­seated emotions.

Rather, behavioral change can

be expected as a consequence of changing beliefs in

relation to grounds for action.

Implications for policy

and practice

Because many juvenile

crimes are committed in the

company of others, crime

rates cannot be accurately

portrayed unless co­offending

is accurately recorded. Yet

inspection of official records

indicates that attention has

not focused on this feature of

crime events. Too often, a

crime is considered to be

solved when a single arrest

has been made.

The Philadelphia study

demonstrates that crime

records should contain accurate information about cooffending. Such accuracy is

necessary if the effects of

policy shifts are to be measured or if differences in crime

rates are to be used as a

basis for such preventive

actions as deploying police

and implementing targethardening measures.

Co­offenders

may learn

through the

influence of

violent

accomplices

that violence

can be an

effective

means for

getting

money or

satisfying 

other desires.

11
RESEARCH IN BRIEF / DEC. 05

CONSTRUCT T

Several theories have been introduced to explain how people learn from

their environments. Many of these involve an assumption that learning

takes place in response to receiving rewards or avoiding punishments

ment, based on perceptions and experiences.a

actions as appropriate partially through finding that others think it normal to commit crimes. It follows that juveniles would be more likely to

consider violent behavior to be appropriate when committing crimes if

their companions consider violence appropriate.

Construct Theory differs from other theories purporting to explain crimipotentiating

reasons provide the impetus for action. For example, in the case of cowhen committing crimes. This belief becomes a potentiating reason for

Some interventions may enhance the effects of co­offending by placing

youths in groups that unintentionally provide negative peer learning.

Peer values that encourage deviant behavior among misbehaving

b

demonstrating that juvenile offenders are influenced by accomplices

who had been violent in prior crimes, even though the present crime

was not violent.

Motivation and Delinquency

(1997): 1–43. 

2001, published in Evidence­Based Policies and Indicator Systems, Conference Proceedings,

University of Durham, England, 2002: 186–192.

HEORY

for specific types of actions. Other learning theories refer to the frequency of encountering particular types of behavior. McCord’s learning

theory—Construct Theory—explains an individual’s intentional actions

as the natural result of how that individual constructs his or her environAccording to Construct Theory, delinquents learn to classify criminal

nal behavior in that it does not rest on implied or stated feelings or emotions. Rather, it relies on an empirical judgment that 

offending, Construct Theory holds that an 11­year­old delinquent often

accepts a (usually older) companion’s belief that violence is justifiable

the youth’s own actions.

youths can provide potentiating reasons for continued misbehavior.

The Philadelphia study validates Construct Theory, at least in part, by

Notes

a. See McCord, J., “He Did It Because He Wanted To . . . ,” in  , ed.

W. Osgood, Nebraska Symposium on Motivation, Lincoln, NE: University of Nebraska Press, 44

b. See McCord, J., “Crime Prevention: A Cautionary Tale,” presentation at the Third International Inter­Disciplinary Evidence­Based Policies and Indicator Systems conference, July

12
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

Perhaps the greatest challenge for intervention is to

target youthful co­offenders

in a way that reduces the

likelihood that they will develop attitudes that promote

crime. The study’s findings

imply that lessons of violence

are learned “on the street,”

where knowledge is passed

along through impromptu

social contexts, including

those in which offenders

commit crimes together.18

Interaction among delinquent

peers apparently serves to

instigate crimes and to escalate their severity.

More research on this issue

is warranted, especially studies that measure peer influence on intentional action,

track the selection of accomplices across multiple crimes,

examine the learning

processes involved in the

transfer of violence across

offenders, and identify individual offenders who may be

particularly susceptible to (or

unaffected by) the influence

of violent accomplices.

When developing and evaluating strategies designed to

prevent or reduce violence,

practitioners and evaluators

may want to consider cooffending patterns, individuals’

choices of accomplices, and

factors that increase the risk

of co­offending, especially

STUDY METHODOLOGYa

A random number generator identified 400 offenders from

police tapes listing 60,821 juvenile arrests in Philadelphia

during 1987. Half the sample was drawn from a list of

offenses the police had recorded as solo offenses and the

other half from a list of co­offenses. If an offender’s court

record could not be found for the listed offense or if the

offender had been previously selected, another crime was

drawn, again using a random number generator, and that

offender became part of the sample. The complete juvenile

criminal records were gathered for all 400 offenders in the

sample. Adult records were traced through 1994. Accomplices were traced for the 335 randomly selected offenders

who had committed at least one co­offense.

Analyses rely on data from court folders, which contained

witness, complainant, police, and co­offender reports. A

comparison between the court records and police tapes

indicated that police records systematically undercounted

co­offending.

Some information about the number of offenders was

available in more than 95 percent of the incidents. When a

range was given, researchers estimated conservatively,

taking the lower number. When “group” was mentioned

with an unspecified number of offenders, the number was

coded as 3.

A crime was considered to be violent if the offenders were

accused of murder, attempted murder, rape, robbery,

aggravated assault, simple assault, terroristic threatening,

intimidating a witness, prowling, or cruelty to animals, or if

the complainant, a witness, or the victim reported violence.

By these criteria, 38 percent of the crimes were violent.

Crimes committed by groups were more likely to be

violent.b

Notes

a. For a complete description of methodology, see McCord, J., and K.P.

Conway, “Patterns of Juvenile Delinquency and Co­Offending,” in Crime 

and Social Organization, vol. 10 of Advances in Criminological Theory, ed. 

E. Waring and D. Weisburd, New Brunswick, NJ: Transaction Publishers,

2002: 15–30.

b. Forty­three percent of crimes committed by groups and 32 percent committed by pairs were violent.

among very young offenders.

13
RESEARCH IN BRIEF / DEC. 05

Notes

1. A 1928 study found that 82 percent of juveniles brought to court in

Cook County, Illinois, committed

their offenses as members of

groups. See Shaw, C.R., and H.D.

McKay, Juvenile Delinquency and

Urban Areas, revised edition,

Chicago: University of Chicago

Press, 1969 (first published 1942).

For studies that focused on group

processes to try to understand juvenile delinquency, see Cohen, A.K.,

Delinquent Boys, Glencoe: Free

Press, 1955; Cloward, R.A., and L.

Ohlin, Delinquency and Opportunity,

New York: Free Press, 1960; and

Short, J., and F.L. Strodtbeck, Group

Process and Gang Delinquency,

Chicago: University of Chicago

Press, 1965.

2. See Carrington, P.J., “Group Crime

in Canada,” Canadian Journal of

Criminology (July 2002): 277–315;

Hockstetler, A., “Opportunities and

Decision: Interactional Dynamics in

Robbery and Burglary Groups,”

Criminology 39 (3) (2001): 737–763;

McCarthy, B., J. Hagan, and L.E.

Cohen, “Uncertainty, Cooperation

and Crime: Understanding the

Decision to Co­Offend,” Social

Forces 77 (1) (1998): 155–184;

Weerman, F.M., “Co­Offending as

Social Exchange: Explaining

Characteristics of Co­Offending,” The

British Journal of Criminology 43 (2)

(2003): 398–416.

3. Maguire, K., and Pastore, A.L.,

Sourcebook of Criminal Justice

Statistics, 2001, Washington, DC:

U.S. Department of Justice, Bureau

of Justice Statistics, 2003, NCJ

196438. Calculations have omitted

“mixed” and “not known.”

4. Supplemental Homicide Reports

are part of the FBI’s Uniform Crime

Reporting system. See also Snyder,

H.N., and M. Sickmund, Juvenile

Offenders and Victims: 1999 

National Report, Washington, DC:

U.S. Department of Justice, Office 

of Juvenile Justice and Delinquency

Prevention, 1999. 

5. Bureau of Justice Statistics,

Sourcebook of Criminal Justice

Statistics, 1998, Washington, DC:

U.S. Department of Justice, 1999,

NCJ 176356.

6. See Reiss, A.J., Jr., “Co­Offending

and Criminal Careers,” in Crime 

and Justice, vol. 10, ed. N. Morris 

and M. Tonry, Chicago: University 

of Chicago Press, 1988: 117–170.

7. See Hindelang, M.J., “With a 

Little Help From Their Friends: 

Group Participation in Reported

Delinquency,” British Journal of

Criminology 16 (1976): 109–125; and

Reiss, A.J., Jr., and D.P. Farrington,

“Advancing Knowledge About CoOffending: Results From [a]

Prospective Longitudinal Survey of

London Males,” Journal of Criminal

Law and Criminology 82 (1991):

360–395. Also, delinquents in cooffending groups studied in Japan

reported that they committed more

crimes together than alone. See

Suzuke, S., Y. Inokuchi, K. Watanabe,

J. Kobayashi, S. Okela, and 

Y. Takahashi, “Study of Juvenile 

Co­offending,” Reports of the

National Research Institute of Police

Science 36 (1995): 2, 64.

8. Before attention was drawn to cooffending, high recidivism rates had

been linked with offenders who

were particularly young when they

14
CO­OFFENDING AND PATTERNS OF JUVENILE CRIME

began to commit crimes. See

McCord, J., and K.P. Conway,

“Patterns of Juvenile Delinquency

and Co­Offending,” in Crime and

Social Organization, vol. 10 of

Advances in Criminological Theory,

ed. E. Waring and D. Weisburd, 

New Brunswick, NJ: Transaction

Publishers, 2002: 16.

9. Property crimes were burglary,

vehicle theft, theft other than 

vehicle, arson, vandalism, criminal

trespass, forgery or counterfeiting,

embezzlement, fraud, and risking or

causing a catastrophe. Violent crimes

were murder, attempted murder,

rape, robbery, aggravated assault,

simple assault, terroristic threatening, intimidating a witness, prowling,

and cruelty to animals.

10. Index crimes are eight categories

of serious crime collected by the

FBI’s Uniform Crime Reporting

Program. Violent Index crimes are

homicide, criminal sexual assault,

robbery, and aggravated assault/

battery. Property Index crimes are

burglary, theft, motor vehicle theft,

and arson.

11. If all young criminals spend about

5 years actively committing crimes,

only those arrested before their 13th

birthdays would spend all their criminal years as juveniles. To compensate for this potential bias, individual

crime rates were computed for both

solo offenses and co­offenses, on

the assumption that once a juvenile

committed a crime, he or she would

remain a delinquent until the age of

18. Whatever bias this computation

introduced affected solo and cooffending rates alike.

12. The ethnic identity of co­offenders

and accomplices matched for 96 percent of black offenders, 83 percent 

of white offenders, and 83 percent 

of Hispanic or other offenders. Researchers traced the criminal histories

of 396 of the accomplices, a success

rate of 77 percent.

13. Sixty­three percent were

younger, 19 percent were older, 

and 18 percent were the same 

age or very close.

14. X 2

(1)=5.626, p<.02.

15. For discussion of this issue, see

Dishion, T.J., J. McCord, and F.

Poulin, “When Interventions Harm:

Peer Groups and Problem Behavior,”

American Psychologist 54 (9) (1999):

1–10.

16. X 2

(1)=9.065, p<.003.

17. Case studies and self­report 

data converge to suggest that 

delinquent groups socialize their

members in ways that encourage

and value violence. 

18. See “Construct Theory” sidebar;

also see McCord, J., “Understanding

Childhood and Subsequent Crime,”

Aggressive Behavior 25 (1999):

241–253.

15
The National Institute of Justice is the

research, development, and evaluation

agency of the U.S. Department of Justice.

NIJ‘s mission is to advance scientific research,

development, and evaluation to enhance 

the administration of justice and public safety.

NIJ is a component of the Office of Justice

Programs, which also includes the Bureau

of Justice Assistance, the Bureau of Justice

Statistics, the Office of Juvenile Justice

and Delinquency Prevention, and the

Office for Victims of Crime.