ROC / AUC Analysis
Definition
Receiver Operating Characteristic / Area Under the Curve analysis; the statistical method used to measure the discriminative accuracy of a linkage system, producing a classification accuracy figure that can be reported as an error rate in court.
- Full name
- Receiver Operating Characteristic / Area Under the Curve analysis
- Measures
- Discriminative accuracy of a linkage system
- Output
- Classification accuracy figure reportable as an error rate
- Applied in
- Serial-offending linkage analysis
Common questions
Why does a linkage analyst need an error rate figure at all?+
Courts increasingly expect quantified reliability for pattern-matching methods, following scrutiny of subjective forensic disciplines, so a stated AUC-derived error rate lets the analyst support a linkage opinion with a measurable accuracy claim rather than an unquantified assertion.
What AUC value would be considered strong evidence of genuine linkage?+
There is no universal courtroom threshold, but values well above 0.5 (chance) and approaching 1.0 indicate the linkage features reliably separate same-offender from different-offender case pairs in the validation dataset used.
Does a high AUC in a validation study guarantee accuracy in a specific case?+
No. AUC reflects performance across a dataset of case pairs, and its relevance to an individual case depends on how representative that dataset is of the offence type, jurisdiction, and modus operandi features being compared.
Related terms
- Behavioural Consistency
- The tendency of a serial offender to repeat the same distinctive behaviours across multiple offences; one of the two necessary conditions for...
- Behavioural Distinctiveness
- The property that the consistent behaviours in question are rare enough across unrelated offenders that shared possession of them cannot easily be...
- Linkage Analysis
- The investigative and forensic method of determining whether two or more crimes were committed by the same person, based on the presence...
- Modus Operandi (MO)
- The functional, learned behaviours the offender uses to commit the offence: how to gain entry, control the victim, complete the act, and...
- Signature
- Psychologically expressive behaviours that go beyond what's needed to complete the offence: posing the body, ritual acts, taking trophies, leaving messages. Signature...
- ViCLAS
- Violent Crime Linkage Analysis System; the RCMP-developed database capturing 168 behavioural and physical fields from serious violent crimes in Canada and adopted...