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Just
ice
Mod
ellin
g@
Grif
fith
1
Juvenile Offending Trajectories
A Queensland Study
Just
ice
Mod
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Grif
fith
2
Presentation
• Background
• Current study
• Results
• Limitations and future research
• Conclusions
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Criminal Careers
• Based on longitudinal cohort studies
• Exploring initiation, frequency, duration,specialisation, escalation and desistance
• Focus on identifying offender sub-populations
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Identifying chronic offenders
• E.g. Wolfgang et. al. (1975)– Chronics = >5 offences
• Farrington et. al. (1987)– ‘Frequents’ and ‘Occasionals’
• Moffitt et. al. (1993)– ‘Life course persistent’ and ‘adolescent-
limited’ offenders
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Identifying chronic offenders
• Offending trajectories incorporate bothprevalence and duration of offending
• Semi-parametric group-based method(SPGM) groups together offenders that havesimilar offending trajectories
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Cohort
• People born in 1983 or 1984 with one or morefinalised court appearances in Queensland
• Included 4,470 young people (23%Indigenous, 77% male)
• Offending (cautioning and court) modelledbetween the ages of 10 and 16
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Offending TrajectoriesAge-Crime Curve
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Age
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Offending TrajectoriesExample trajectories
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10 11 12 13 14 15 16Age
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Current study
• Develop a trajectory model of juvenileoffending
• Explore correlates of trajectory membership
• Assess predictive validity of trajectories
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Trajectory model
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10 11 12 13 14 15 16
Age
App
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nces
/cau
tions
Group 1 (Late onset)
Group 2 (Adolescent limited)
Group 3 (Chronic)
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0
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10 11 12 13 14 15 16
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Late Onset Group
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Late Onset Group
• Included more than two-thirds of the cohort
• Average of 2.3 contacts as juveniles
• Responsible for 40% of the entire cohort’soffending
• Average 15.3 years old at first contact
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0
0.5
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1.5
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10 11 12 13 14 15 16Age
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nces
/cau
tions
Adolescent Limited Group
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Adolescent Limited Group
• Included 20% of the cohort
• Average of 3.9 contacts as juveniles
• Committed 23% of the offences committed bythe whole cohort
• Average 13.8 years old at first contact
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Chronic Group
0
0.5
1
1.5
2
2.5
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10 11 12 13 14 15 16Age
App
eara
nces
/cau
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Chronic group
• Included just over one-tenth of the cohort
• Average of 10.5 contacts as juveniles
• Responsible for 33% of the entire cohort’soffending
• Average 13.3 years old at first contact
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• Six factors explored:– Sex– Indigenous status– Remoteness of residence– Socio-economic disadvantage (of area of
residence)– Child protection history– First court outcome
Factors associated with trajectories
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Factors associated with chronicoffending
– Males more than twice as likely as femalesto follow ‘chronic’ trajectory
– Indigenous offenders between 3 and 5times as likely as non-Indigenous to follow‘chronic’ trajectory
– Young people with child protectionsubstantiations were 2 – 4 times morelikely to follow ‘chronic’ trajectory
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Factors associated with chronicoffending
7%22%42%CP History
51%71%87%Male
5%23%51%Indigenous
% EntirePopulation
% Offendingcohort
% Chronicgroup
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Predictive validity of trajectories
• Relationship between juvenile offendingtrajectory and adult offending
• For this study, adult offending was based onadult court appearances and was simplycoded as a yes/no variable
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Adult offending
Adult offending
Yes NoOffending Trajectory
Groupn % n %
Late Onset 1,102 36.0 1,956 64.0Adolescent Limited 308 33.4 615 66.6Chronic 329 67.3 160 32.7Total 1,739 38.9 2,731 61.1
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Adult offending
• When sex, Indigenous status, remoteness andSED, child protection and first court outcomewere controlled for in a logistic regressionmodel:
– Chronics were 2.7 times more likely toprogress than late onset offenders
– Chronics were 3.3 times more likely toprogress than adolescent limited offenders
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Adult Offending
• Of the offenders who did go on to adultoffending:
– Late-onset juveniles averaged 4.1 adultcourt appearances
– Adolescent-limited juveniles averaged 3.6court appearances
– Chronic juveniles averaged 6.3 courtappearances
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Findings
• Trajectory model similar to U.S., U.K. and NewZealand models
• Consistency of results adding evidence to amodel of offending that includes two or moresubpopulations of offenders
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International comparisons
Study # offendingtrajectories
# chronictrajectories
Cambridge study of delinquent development 3 2Christchurch Health and Development Study 3 1Philadelphia Study 2 4 3Juvenile delinquency and adult crime 1942 4 2Juvenile delinquency and adult crime 1949 3 1Juvenile delinquency and adult crime 1955 4 2Queensland offending cohort 3 1
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Findings
• Expected differences between males andfemales; Indigenous and non-Indigenousoffenders
• Child protection history strongly related tooffending trajectory
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Findings
• Offending trajectories strongly predict adultoffending at an aggregate level
• Chronic juveniles are twice as likely to appearas adults as other juveniles and appear morefrequently as adults.
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Limitations of study
• Short time frame
• Limited range of factors available
• Sample attrition
• Use of official data for offending
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Future research
• Extend study into adult offending
• Explore costs of juvenile chronic offenders toGovernment
• Studies of how interventions/social changes(such as marriage, employment etc) affecttrajectory group membership