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

Samantha.lundrigan@vuw.ac.nzSamantha.lundrigan@vuw.ac.nz