The estimation of total population size for various phenomena of crime is an
important factor critical for criminal justice policy formulation and criminological
theory development. In this paper, methods are discussed for estimating the
size of a criminal population from police records. Capture-recapture analysis
techniques, borrowed from the biological sciences, are used to predict the size
of population for migrating (or fleeing) fugitives and for street prostitutes.
Heterogeneity and behavioral responses to previous police encounters are identified
as major complicating factors. The basic problem is that the police records
are virtually unaffected by a potentially large pool of cryptic criminals. It is
shown how independently collected auxiliary data can address this problem.
