A Failure to Find Empirical Support for the Homology Assumption in Criminal Profiling

A fundamental assumption in criminal profiling is that criminals who exhibit similar crime scene actions have similar background characteristics. We tested this so-called homology assumption by first classifying, with pre-existing typologies, a sample of arsons (N = 87) and robberies (N = 177) into different crime types and then comparing the background characteristics of criminals who committed the various crime types. Results showed that using pre-existing typologies to classify the crimes into mutually exclusive types was not easily accomplished. Notwithstanding classification difficulties, the homology assumption was violated in 56% of the comparisons of background characteristics between the different arson types and in 67% of the comparisons of background characteristics between the different robbery types. Overall, 73% of the effect sizes for the associations between crime type and background characteristics were low to moderate (V < .3; d < .2). The implications of these findings for profiling practices are discussed.

Brent SnookEmail: