R v Thomas: Clarifying Sentencing Parity Where Co-Defendants Straddle the 16/19 Age Threshold

Introduction

In Thomas, R. v ([2025] EWCA Crim 718) the Court of Appeal (Criminal Division) revisited the thorny issue of sentence parity where co-defendants fall on opposite sides of the 18-year “adult” cliff-edge set by Schedule 21 of the Sentencing Act 2020. The applicant, aged 19 at the material time, sought leave to appeal a life sentence with a 25 year 3 month minimum term imposed for murder committed “for gain” during a robbery spree with his 16-year-old half-brother, Nyron. The appeal contended that the minimum term was “manifestly excessive” when compared with Nyron’s 19 year 10 month tariff and in light of the applicant’s immaturity and secondary role. Mr Justice Cavanagh, giving judgment, refused leave. In doing so the Court elaborated on, and in effect limited, the parity guidance recently laid down in R v Kamarra-Jarra [2024] EWCA Crim 198 where age gaps were months rather than years.

Summary of the Judgment

The Court confirmed that Parliament’s statutory starting points (30 years for adults; 20 years for 15–16-year-olds) must be respected even where that generates pronounced disparities.
Where the chronological age gap is substantial (≈2½ years here), a significant difference in minimum terms is not necessarily unfair.
The sentencing judge had properly discounted the adult starting point by almost five years to reflect the applicant’s immaturity and to narrow the gap with Nyron’s tariff.
The resulting 25 year 3 month minimum term—also incorporating two robberies—was not “manifestly excessive”.
Permission to appeal was therefore refused.

Detailed Analysis

1. Precedents Cited

The judgment canvasses a line of authorities on youth, maturity and parity:

R v Kamarra-Jarra [2024] – Primary guidance on smoothing disparities where one defendant is just under and another just over 18. Emphasises looking beyond chronological age.
R v Peters [2005] & R v Matthews [2005] – Early statements that turning 18 is not a “sentencing cliff-edge”.
R v Clarke [2018] – Lord Burnett CJ’s reaffirmation that maturity develops past 18.
R v ZA [2023] – Neuroscientific basis for treating young adults (18–25) differently.
R v Taylor (Joel) [2017] & AG Ref (Brown & Carty) [2007] – Older parity cases urging judges to minimise unjustified gaps between co-defendants.
AG Ref (SK) [2022]

The Court traced how each authority converges on a single point: maturity, not age alone, drives culpability. However, those cases did not override Parliament’s express 10-year step for murder-for-gain.

2. Legal Reasoning of the Court

Statutory Primacy: Schedule 21 sets mandatory starting points. Courts may adjust downwards, but must begin with Parliament’s scheme. For a 19-year-old it is 30 years; for a 16-year-old, 20 years.
Evaluating Parity:
- Parity is not an end in itself; it is subsumed within overall fairness.
- Kamarra-Jarra applies most strongly where the chronological gap is narrow (mere months). Here, a 2.5-year gap sits across a legislatively mandated 10-year step.
Maturity Discount: The judge accepted psychological evidence that the applicant presented below his chronological age and reduced the adult starting point by ~20% (30 yrs → 24 yrs).
Totality & Additional Harm: A further 15-month uplift was applied for the two earlier robberies, consistent with the principle that the overall sentence must reflect the total criminality.
Secondary Participation: While the applicant did not wield the knife, the jury had found he intentionally encouraged serious violence knowing his brother carried a large blade. Secondary liability in murder attracts the same mandatory life sentence; culpability is tempered only at the minimum-term stage.

3. Impact on Future Cases

Thomas will likely shape sentencing in three ways:

Scope of Kamarra-Jarra: The Court signals that Kamarra-Jarra parity adjustments are limited when age differences are greater and statutory starting points diverge sharply.
Youth Discounts: Judges retain discretion to reflect immaturity but must articulate why any reduction still honours Parliament’s framework.
Secondary Role in Murder: Even where the older participant is not the killer, substantial tariffs remain appropriate if they initiated or encouraged the violence.

Complex Concepts Simplified

Minimum Term: The period an offender must spend in custody before first becoming eligible for parole on a life sentence.
Murder “for gain”: A homicide committed to obtain property; automatically classed as “particularly high seriousness” (30-year starting point).
Schedule 21 (Sentencing Act 2020): Statutory matrix prescribing starting points for murder tariffs based on age and aggravating features.
Section 45 YJCEA 1999 Reporting Restriction: Prohibits identifying child victims/witnesses.
Totality Principle: Ensures the aggregate sentence for multiple offences is proportionate to overall wrongdoing.
Leave to Appeal Against Sentence: Permission stage designed to filter unarguable sentence appeals.
Manifestly Excessive: A sentence so high that no reasonable judge could have imposed it, considering the facts and guidelines.

Conclusion

R v Thomas reinforces that statutory starting points are the bedrock of murder sentencing and that large chronological age gaps can legitimately translate into pronounced tariff differences—even where the older defendant is immature and less directly violent. The decision narrows the ambit of Kamarra-Jarra, confirming that its parity levers are strongest where ages are adjacent. Practitioners must therefore marshal compelling evidence of maturity—not merely youth—to justify deviations from Parliament’s framework, and should anticipate that courts will tolerate wider differentials when defendants straddle the 18-year threshold. Ultimately, Thomas offers a clarified roadmap for balancing statutory imperatives, offender maturity, and sentence parity in complex multi-defendant murders.