Co-convictions are court convictions made at the same time as a more serious conviction. Their importance has been little recognized.We investigate their value using data on two separate serious crimes. Taking official conviction careers in England and Wales (1979-2001) for blackmail (n = 5774) and kidnapping offenders (n = 7291), we considered how much information on co-convictions is normally overlooked, and how knowledge of co-convictions contributes to predicting serious recidivism. We identified that co-convictions were pervasive, with 54 per cent of convictions for blackmail and 77 per cent for kidnapping having co-convictions. Co-convictions provided extra explanatory power in predicting the risk of a subsequent sexual or violent offence for both blackmail and kidnapping. For blackmail, most types of co-conviction were associated with a significantly raised relative risk, whereas for kidnapping, only co-convictions which were not acquisitive, sexual or violent had a significantly raised relative risk. We concluded that co-convictions are a useful measure of short-term specialization and are important when predicting serious recidivism.

Prediction Secondary convictions Violent recidivism Sexual recidivism Co-convictions Specialization

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