Jb. Copas et F. Heydari, ESTIMATING THE RISK OF REOFFENDING BY USING EXPONENTIAL MIXTURE-MODELS, Journal of the Royal Statistical Society. Series A. Statistics in society, 160, 1997, pp. 237-252
In deciding whether to release a prisoner on parole, the Parole Board
as provided with a statistical score which estimates the chance that t
he prisoner will reoffend within the period of time that he or she wou
ld otherwise be in prison. This score is based on a survival analysis
of data on a sample of releases from long-term prison sentences. To ca
pture most reoffences which occur within 2 years of release, follow-up
must continue for at least 3 years to allow for the delay between off
ence and conviction. We reanalyse the data by using a model which expl
icitly allows for this delay. The new analysis can be applied to data
with a substantially shorter length of follow-up. This means that risk
scores can be constructed from more up-to-date data and at less cost.