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Spatial Characteristics of Spatial Characteristics of Serial Sexual Assault in New Serial Sexual Assault in New ZealandZealand
Dr Samantha LundriganDr Samantha Lundrigan
Victoria University of WellingtonVictoria University of Wellington
Research AimsResearch Aims
To examine the characteristics of New To examine the characteristics of New Zealand sex offenders with respect to:Zealand sex offenders with respect to: Spatial behaviourSpatial behaviour Consistency in offence environment Consistency in offence environment
selectionselection
The New Zealand ContextThe New Zealand Context
4million in a land 4million in a land area of 268,680 km area of 268,680 km sq.sq.
92% rural land, 8% 92% rural land, 8% built up.built up.
2001 population 2001 population density of 14 per km density of 14 per km sq. sq.
Data collectionData collection
Police files – New Zealand Police Police files – New Zealand Police Criminal Profiling SquadCriminal Profiling Squad
Crime scene, background and Crime scene, background and geographical information coded and geographical information coded and mappedmapped
The sampleThe sample
76 serial offenders76 serial offenders Between 1970 and 2002Between 1970 and 2002 Collectively 270 offences (mean of 3.5 per Collectively 270 offences (mean of 3.5 per
series)series) CharacteristicsCharacteristics
70% strangers, 20% friend/associate, 1% 70% strangers, 20% friend/associate, 1% previous partnerprevious partner
Mean age of 23 (12-60)Mean age of 23 (12-60) 53% NZ Maori, 21% NZ European, 18% Pacific 53% NZ Maori, 21% NZ European, 18% Pacific
Island PeopleIsland People
ResultsResults
Journey to crimeJourney to crime
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Distance from base (km)
0
50
100
150
Nu
mb
er o
f o
ffen
ces
Mean = 7.404Std. Dev. = 12.47579N = 254
Criminal Criminal RangeRange
0.00 50.00 100.00 150.00 200.00 250.00 300.00
maxdist (km)
0.00
10.00
20.00
30.00
40.00
50.00
min
dis
t (k
m)
r = 0.470 (P<.001)
Spatial patternSpatial pattern
Marauders 37%, Commuters 34%, Transients 29%Marauders 37%, Commuters 34%, Transients 29%
Measure Marauders (median Marauders (median km)km)
CommutersCommuters
(median km)(median km)Mean distance travelled** 2.362.36 5.785.78
Min distance travelled* 0.180.18 0.910.91
Maximum distance travelled** 4.754.75 11.7311.73
Mean Interpoint Distance 12.8912.89 4.404.40
Max distance between offences 20.2820.28 8.738.73
Min distance between offences*
01.1701.17 0.320.32
* p<.05 ** p<.01
Environmental Environmental consistencyconsistency
VariablesVariables Type of contact siteType of contact site Victim transportationVictim transportation Day of weekDay of week Time of dayTime of day Distance to offenceDistance to offence Area typeArea type Land useLand use Deprivation scoreDeprivation score
Consistency scoreConsistency score
Mean 4.56, Median Mean 4.56, Median 4.79, Standard 4.79, Standard deviation 1.70deviation 1.70
Min 1, Max 8Min 1, Max 8
ScoreScore NN Cum%Cum%
0≤ 2 0≤ 2 88 10.510.5
2≤ 4 2≤ 4 2424 42.142.1
4≤ 6 4≤ 6 3131 82.982.9
6≤ 8 6≤ 8 1313 100.0100.0
Consistency scoreConsistency score
44 (57%) of offenders scored above 4, 44 (57%) of offenders scored above 4, the score midpoint.the score midpoint.
Proportional chance expected 2.5% of Proportional chance expected 2.5% of offenders (z=45.42, p<.0001).offenders (z=45.42, p<.0001).
Future ResearchFuture Research
More detailed analysis of environmental More detailed analysis of environmental characteristics characteristics
Offender-offence environment Offender-offence environment consistencyconsistency
Implications for Geographic profiling Implications for Geographic profiling systemssystems
Thank youThank you
Dr Samantha LundriganDr Samantha LundriganInstitute of CriminologyInstitute of Criminology
Victoria University of WellingtonVictoria University of Wellington
WellingtonWellington
New ZealandNew Zealand
[email protected]@vuw.ac.nz