Scottish prison population projections: December 2024

Conclusions

As of 6th December 2024, the prison population was 8,260. The modelling indicates a projected range for the average daily total prison population of between 7,950 and 8,900 in April 2025.

When implemented in February 2025, the measures in the Prisoners (Early Release) (Scotland) Bill should reduce the sentenced population by around 5%[1]. However, it should be noted that these prison population projections do not include the effects of the Bill (although it has been passed, Royal Assent is required for it to become an Act); rather they project the population if recent trends were to continue. If the impact of the bill were realised then it is expected it would result in a reduction to the sentenced population of between 260 and 390 (after accounting for uncertainty in the size and composition of the sentenced population)[2]. The next issue of these projections will include reporting on the expected impact of the Bill, by which time more information will be available to indicate the size of the sentenced population during implementation.

The rapid rise in the prison population after the June/July 2024 ER came at a time when the population was already relatively high following substantial growth in 2023/2024. In the first publication of June 2023, only low, central and high court throughput scenarios were reported. There is now more evidence that remand arrivals tend to rise to a peak during the period from around February to August, then are lower around September to December (see Figure 2). Hence, in this update to the projections it is assumed that average monthly remand arrivals during February to April 2025 will be similar to what they were during February to July 2024. Over the course of the next few months, remand arrivals, sentenced arrivals and case conclusion levels will be monitored to assess with which scenarios the actual prison population numbers are most closely aligned.

For several reasons, modelling the future prison population using the microsimulation becomes less accurate the further ahead it is projected (whether due to systematic errors in the model, inaccurate assumptions due to unforeseen circumstances, or due to changed circumstances that the model is not built to account for). Experience to date suggests that a maximum projection period of six months allows for reliable projections.

As previously highlighted, the key factors impacting changes in the prison population in the short term will be the flows into and out of the remand and sentenced populations. This is influenced by the court recovery programme, for example the resource re-allocation from summary to solemn which took place in April 2023. The modelling assumes that there will be no further changes to the number of court rooms allocated to summary and solemn procedure until at least May 2025.[3].