Clarifying the Limits of the Overwhelming Supervening Act Defence in Secondary Liability Cases

Introduction

The case of Ayre & Ors, R. v ([2025] EWCA Crim 255) presents a significant development in the application of the doctrine of secondary liability within criminal law, particularly as it relates to whether a defendant can rely on an overwhelming supervening act (OSA) to negate liability. The incident in question occurred on the night of 12 July 2022 when a Ford Mondeo was deliberately driven into a group of pedestrians, resulting in fatal consequences (the death of Andrew Flamson) and grievous injuries (to Damien Corbett), as well as lesser injuries to two other individuals. The parties involved include the principal offender, Donald, and his co-accused—Callum Ayre, Samuel Henneberry, and Carl Tomlinson—whose actions in a rapidly unfolding, violent confrontation culminated in a fatal collision. This judgment, delivered by Lord Justice Holroyd, not only reaffirms established principles from previous cases but also clarifies the applicable scope of the OSA defence in scenarios involving secondary liability.

Summary of the Judgment

The England and Wales Court of Appeal (Criminal Division) upheld the trial judge’s decision to reject the defence of OSA, thereby confirming the conviction of Ayre, Henneberry, and Tomlinson on charges including manslaughter, maliciously inflicting grievous bodily harm, and assault occasioning actual bodily harm. Notably, the judge dismissed submissions that argued the escalation of violence—exemplified by the decision to use a car as a weapon—could be regarded as an overwhelming intercurrent event that might erase the earlier common intention or assistance provided in the criminal plan. The judgment elaborated that, under the principles established in R v Jogee and more recently in R v Grant, the defence of OSA is inapplicable when secondary offenders’ actions are contemporaneous and closely linked to the principal offence. This ruling was reached notwithstanding the appellants’ arguments that any departure from the original plan should have allowed the defence to be considered by the jury.

Analysis

Precedents Cited

The judgment extensively cites two landmark cases:

• R v Jogee [2016] UKSC 8 – This case re-examined the requirements for secondary liability, emphasizing that for an accessory to be found liable, it is necessary to prove that the defendant intentionally encouraged or assisted the principal in committing the offence. The ruling clarified that the defence of OSA can only apply where the accessory’s actions have become so disconnected from the principal act that they no longer contributed to the outcome.
• R v Grant [2021] EWCA Crim 1243 – In Grant, the court firmly held that departures from the agreed plan, while potentially relevant for reckoning causation, are assessed in terms of whether they affected the continuity of the shared criminal intention. The application of OSA is distinct from issues of causation, and a mere escalation of violence does not suffice to trigger OSA.

Both these cases serve to firmly delineate the scope of secondary liability. In the current judgment, the Court of Appeal reinforced the position that the accessory’s contemporaneous involvement—evidenced by the immediate sequence of events leading to the collision—meant that the OSA defence was not applicable.

Legal Reasoning

The court’s reasoning is anchored in two critical questions: whether the secondary offender intentionally assisted or encouraged the principal’s criminal act, and whether that intent was contemporaneous with the principal’s actions. The judge found that:

• The actions of Ayre, Henneberry, and Tomlinson were not so attenuated or temporally remote as to be considered merely historical background. Instead, their immediate involvement—getting into the car, carrying weapons, and following Donald—established a clear shared intention to engage in unlawful violence.
• The escalation (switching from verbal threats to a premeditated violent act using a car as a weapon) was not an unexpected departure but rather a natural outcome of their joint plan. The judge underscored that even if the vehicle’s use instead of a traditional weapon was not initially contemplated in the plan, such a variation does not exonerate the participants from liability.

In rejecting the OSA defence, the court emphasized that the relevant legal standard does not consider a change in the method or an escalation of violence as grounds for dismissing secondary liability, provided the accessory’s assistance was current and integral to the execution of the plan. The judge even reiterated that a mere difference in the weapon used or the degree of violence does not diminish the accessory’s legal culpability.

Impact on Future Cases and Legal Practice

This judgment has significant implications for future cases involving secondary liability and the defence of OSA. Key impacts include:

• Narrowing of the OSA Defence: The ruling affirms that the defence of OSA will only apply in exceptional circumstances where there is clear evidence of an overwhelming, unforeseeable intervening act. Practitioners will need to construct a strong evidential basis before arguing that the accessory’s actions have become “spent” by a supervening event.
• Clarification of Intent Standards: The court’s insistence on the requirement for contemporaneous intent ensures that future assessments of secondary liability remain focused on the accessory’s active participation in the evolving criminal act.
• Guidance for Jury Directions: The detailed route to verdict provided by the trial judge will assist juries in dissecting complex issues of shared criminal intention, particularly in fast-developing cases involving multiple participants and evolving plans.

Overall, the ruling provides enhanced clarity on where the boundary lies between anticipated escalation and the unforeseeable, fundamentally disconnecting events that might otherwise be argued as negating the original criminal intent.

Simplification of Complex Legal Concepts

The judgment deals with several complex legal concepts, which we can simplify as follows:

• Secondary Liability: This occurs when someone is held responsible not as the principal actor but for assisting or encouraging another to commit a crime. What matters is whether the accessory had the requisite (often shared) intent at the time of the crime.
• Overwhelming Supervening Act (OSA): This defence is argued when an unforeseen, intervening event (or escalation) interrupts the original chain of events such that the accessory’s contribution to the crime is effectively “relegated to history.” The court has now clarified that only events so radically disjunctive that they sever the causal connection can warrant its application.
• Encouragement/Assistance: The court insists that for a secondary party to be held liable, there must be evidence that the defendant actively encouraged or assisted the principal’s crime at the time it was being planned or executed. Knowledge of weapon usage or the method of attack, while relevant, is only part of the assessment.

Conclusion

In Ayre & Ors, R. v ([2025] EWCA Crim 255), the Court of Appeal has provided a robust reaffirmation of the principles established by R v Jogee and R v Grant. Through their detailed analysis, the judges made it clear that the use of a car as a weapon and the subsequent escalation in violence did not amount to an overwhelming supervening act that could absolve the accessory defendants from liability. Instead, it was the very contemporaneous and active participation of these defendants in the shared, developing plan that underpinned their convictions.

The case not only reinforces the precise requirements for secondary liability—which necessitate simultaneous intent and assistance—but also signals a narrowing of the OSA defence to truly exceptional circumstances. For legal practitioners, this judgment provides definitive guidance on how to frame arguments concerning joint criminal action and the limitations of intervening events. In a broader context, the ruling enhances the predictability of outcomes in complex criminal cases involving multiple actors, thereby contributing to a more consistent application of the law.

Ultimately, the judgment is a significant milestone in clarifying the parameters of accessory liability and ensuring that the defence of OSA is not misapplied, thereby maintaining the integrity of the legal principles governing joint criminal actions.