Justice Data Lab Results

Langley is delighted that Justice Data Lab results show a positive impact of our interventions on reducing reoffending.

Front page of Ministry Justice report about Justice Data Lab results for Langley House Trust looking at the impact on reducing reoffending

The Ministry of Justice introduced the Justice Data Lab in 2013. It measures the hard outcome results of the voluntary sector when working in Criminal Justice.

231 offenders, all who received support from Langley between 2002 and 2011, were matched against a group of offenders who did not receive support from Langley in that time period.


Langley is delighted that the findings showed that the one year proven re-offending rate* for the 231** offenders who received Langley’s support was 26%, compared with 35% for a matched control group of similar offenders.

Statistical significance testing showed that this difference in the re-offending rates was “statistically significant”. This meant there was confidence that there was a real difference in the re-offending rate for people who received Langley’s support by between 2 and 14 percentage points.***

This underlines the fact that Langley makes a significant difference to people’s lives. While individuals are in our housing, we have a 2.6% reconviction rate.

The results were recently re-run, using Offender Assessment System data (OASys). The OASys is a probation assessment tool which is used to understand the risks and needs of offenders linked to their criminal activity. This provided a more robust picture of the profile of the cohort and included needs such as housing, drugs and alcohol use. The results returned showed similar results to the earlier reports and gave more confidence about the comparison group used. Langley is the first organisation to use the OASys to calculate a more accurate comparison group. For the methodology, click here.

The full report – including statistical clarification – can be found here.

Explanatory notes – Ministry of Justice

*The one year proven re-offending rate is defined as the proportion of offenders in a cohort who commit an offence in a one year follow-up period which was proven through receipt of a court conviction, caution, reprimand or warning during the one year follow-up or in a further six month waiting period. The one year follow-up period begins when offenders leave custody, start their court sentence, or from receipt of their caution.

**231 individuals were matched from a cohort of 775 individuals, whose details were sent to the Justice Data Lab, as described on page 3 of the full report.

***The p-value for this significance test was 0.005. Statistical significance testing is described on page 9 of the full report. All results exclude any individuals who had committed sex offences because of different patterns of offending.