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Linking serial sexual offences: Moving towards an ecologically valid test of the principles of crime linkage
Author(s) -
Woodhams Jessica,
Tonkin Matthew,
Burrell Amy,
Imre Hanne,
Winter Jan M.,
Lam Eva K. M.,
ten Brinke Gert Jan,
Webb Mark,
Labuschagne Gerard,
Bennell Craig,
AshmoreHills Leah,
van der Kemp Jasper,
Lipponen Sami,
Pakkanen Tom,
Rainbow Lee,
Salfati C. Gabrielle,
Santtila Pekka
Publication year - 2019
Publication title -
legal and criminological psychology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.65
H-Index - 57
eISSN - 2044-8333
pISSN - 1355-3259
DOI - 10.1111/lcrp.12144
Subject(s) - optimal distinctiveness theory , similarity (geometry) , jaccard index , sample (material) , psychology , consistency (knowledge bases) , linkage (software) , crime scene , series (stratigraphy) , set (abstract data type) , test (biology) , social psychology , computer science , criminology , cognitive psychology , artificial intelligence , pattern recognition (psychology) , paleontology , biochemistry , chemistry , chromatography , biology , image (mathematics) , gene , programming language
Purpose To conduct a test of the principles underpinning crime linkage (behavioural consistency and distinctiveness) with a sample more closely reflecting the volume and nature of sexual crimes with which practitioners work, and to assess whether solved series are characterized by greater behavioural similarity than unsolved series. Method A sample of 3,364 sexual crimes (including 668 series) was collated from five countries. For the first time, the sample included solved and unsolved but linked‐by‐ DNA sexual offence series, as well as solved one‐off offences. All possible crime pairings in the data set were created, and the degree of similarity in crime scene behaviour shared by the crimes in each pair was quantified using Jaccard's coefficient. The ability to distinguish same‐offender and different‐offender pairs using similarity in crime scene behaviour was assessed using Receiver Operating Characteristic analysis. The relative amount of behavioural similarity and distinctiveness seen in solved and unsolved crime pairs was assessed. Results An Area Under the Curve of .86 was found, which represents an excellent level of discrimination accuracy. This decreased to .85 when using a data set that contained one‐off offences, and both one‐off offences and unsolved crime series. Discrimination accuracy also decreased when using a sample composed solely of unsolved but linked‐by‐ DNA series (AUC = .79). Conclusions Crime linkage is practised by police forces globally, and its use in legal proceedings requires demonstration that its underlying principles are reliable. Support was found for its two underpinning principles with a more ecologically valid sample.