The Costin Discretion: Court of Appeal Confirms No Mandatory Credit for Lost Parole Opportunity of IPP Prisoners

1. Introduction

Costin, R. v ([2025] EWCA Crim 729) is a significant Court of Appeal decision which solidifies how sentencing courts should treat an offender who:

is already serving an Indeterminate Sentence of Imprisonment for Public Protection (“IPP”); and
is subsequently convicted of historic offences which, but for the investigation and trial, might have resulted in earlier parole on the IPP sentence.

The appellant, a former scout leader and teacher, faced 22 counts of indecent assault committed in two distinct periods (1980s and 1990s) against multiple child victims. Although the trial judge imposed an aggregate term of 15 years and 3 months, the core issue on appeal was narrow: should the court reduce that term to reflect the punitive impact on the appellant’s existing IPP sentence—namely, the loss of parole opportunities and additional time spent in closed conditions?

2. Summary of the Judgment

The Court of Appeal (Hilliard J) dismissed the appeal. Key findings were:

The time an IPP prisoner spends in custody prior to sentencing for new offences cannot be credited automatically towards the new determinate sentence.
The sentencing judge retains only a residual discretion—derived from authorities such as R v Ashley—to make some allowance in exceptional circumstances, but the exercise of that discretion is fact-specific and never an entitlement.
In the appellant’s case, refusing any additional credit was reasonable because:
- the appellant’s ongoing risk and entrenched denial of sexual gratification justified continued detention;
- the parole board would have considered the present offences had they been known, likely leading to continued detention in any event; and
- the investigative delay was not “undue” but a consequence of historic victims coming forward over time.
Accordingly, the total sentence of 15 years and 3 months remained “just and proportionate”.

3. Analysis

3.1 Precedents Cited & Legislative Framework

Section 240ZA Criminal Justice Act 2003
Governs credit for time spent on remand. It expressly excludes time spent in custody on other sentences (e.g., recall on licence). The Court used the analogy that an IPP prisoner is in a similar position—no automatic credit.
R v Kerrigan & Walker [2014] EWCA Crim 2438
Illustrates the above statutory position for offenders recalled on licence awaiting sentence for fresh offences.
R v Ashley [2024] EWCA Crim 1456
Clarifies the “residual discretion” to grant a sentencing adjustment where rigid application of s.240ZA would be unjust, particularly in cases of excessive delay or where recall was triggered solely by the new offence.
Criminal Justice Act 2003, s.225 and Legal Aid, Sentencing and Punishment of Offenders Act 2012 (LASPO)
Provide the statutory background to IPP sentences—now abolished prospectively, but still fully operative for those, like Costin, sentenced before 2012.
Sentencing Guidelines (Sexual Offences Definitive Guideline)
Used to identify “present-day” starting points and ranges for historic offences, a standard approach endorsed by the Court.

3.2 The Court’s Legal Reasoning

The Court’s analytic path can be broken into six steps:

Historical Sentencing Calibration: The judge used current guideline categories to produce individual sentence lengths, then applied totality to reach concurrent and consecutive terms.
Risk and Dangerousness Assessments: Despite therapy completions, the appellant still exhibited distorted beliefs (“no sexual gratification”) and high risk to children, which militated against an extended or reduced sentence.
Totality & Proportionality: Two logical clusters of offences (1980s and 1990s) warranted consecutivity, each cluster concurrent within itself.
IPP Interaction: The Court emphasised that an IPP prisoner is lawfully detained on existing risk grounds and that “lost parole opportunity” arguments border on speculation absent evidence the Parole Board would definitely have released him.
Residual Discretion: Drawing on Ashley, the Court accepted that judges can adjust sentences, but only where it would be patently unjust not to. Here, secrecy of the historic offences had given the appellant a de facto advantage for years; once discovered, he cannot claim prejudice.
No Undue Delay: The investigative timeline (2017–2024) was dictated by victims’ gradual disclosures and partial admissions by the appellant. The Court found no state-generated “unjustified delay.”

3.3 Impact of the Judgment

The Costin decision crystallises what might be dubbed the “Costin Discretion”:

When an IPP prisoner faces new historic charges, no automatic credit will be given for time already served or for the loss of parole prospects.
Sentencers must still consider the discretionary adjustment power, but detailed, fact-specific justification is required. The bar is high.
Practitioners can expect more rigorous proof obligations if arguing for sentence mitigation based on parole ramifications. Evidence of certain or near-certain release prospects absent the new offences will be essential.
Victims’ interests remain paramount: historic offences that surface belatedly do not disadvantage the prosecution case—even if the offender already faces indeterminate detention.
Parole Board practice may subtly shift: risk assessments will now explicitly incorporate possible undiscovered historic offending, recognising Costin’s reasoning that such hidden conduct can undermine the accuracy of previous rehabilitation evaluations.

4. Complex Concepts Simplified

Indeterminate Sentence for Public Protection (IPP): A sentence under which the prisoner has no fixed release date. The Parole Board can only release the offender when it is satisfied public safety is assured.
Totality Principle: Courts must look at the overall criminality and ensure the combined sentence is just and proportionate, often by making some sentences concurrent and others consecutive.
Residual Sentencing Discretion: Even where statutes bar credit for time served, judges retain a narrow power to adjust sentences to avoid manifest injustice—this is not a right of the offender.
Historic Sexual Offences: Crimes committed many years earlier. Courts apply modern sentencing guidelines for starting points but adjust for maximums in force at the time of the offences, to avoid retroactive punishment.
Category 1A / 2A etc. (Guidelines): Classifications indicating harm and culpability. “1A” is typically the most serious due to factors such as severe psychological harm or multiple incidents; “3B” indicates lower harm and/or culpability.

5. Conclusion

Costin stands for a clear proposition: an offender’s frustrated parole hopes under a pre-existing IPP sentence do not, by themselves, justify a reduction in a new sentence for serious historic offences. The decision:

aligns IPP-parole situations with recall-on-licence scenarios under s.240ZA CJA 2003;
endorses a high threshold for invoking the residual discretion identified in Ashley;
re-affirms the primacy of public protection and the totality principle in sexual-offence sentencing; and
offers crucial guidance for both prosecutors and defence when navigating the complex overlap between IPP sentences, historic offences, and parole.

Practitioners should now treat the “Costin Discretion” as a robust benchmark: absent exceptional and demonstrable injustice, an IPP prisoner cannot expect any credit for lost parole opportunity when freshly sentenced for historic crimes. The ruling thereby fortifies public confidence that serious child-sexual-offence sentencing will remain proportionate, protective, and immune from speculative reductions.