How not to assess probation performance: Constructing local reconviction rates

Much of the responsibility for securing reductions in offending and reoffending is being devolved to local statutory services. It follows that robust and timely local measures for assessing reoffending must be created. To this end, for the last three years the National Offender Management Service has produced quarterly reconviction reports for individual probation areas based on `snapshots' (cross-sectional samples) of the supervision caseload. An independent examination of the data for the East Midlands Region reveals that the way cases have been selected and followed-up departs from the conventions employed in all previous (`longitudinal') reconviction studies in England and Wales. In particular, the `crosssectional' or snapshot approach led to the `at risk' period varying from one offender to another; and those on longer sentences stood a much greater than usual chance of appearing in several samples over time. This, together with other problems associated with not following a conventional longitudinal approach, leads to the conclusion that it would be unwise to use the quarterly figures produced thus far to draw conclusions about probation areas' performance.