Inchoate offences and accessorial liability

Criminal law extends beyond principal offenders through two mechanisms: inchoate offences criminalise preparatory conduct before the substantive offence occurs (attempts, conspiracy, encouragement/assistance), while accessorial liability captures those who participate in completed offences. The Criminal Attempts Act 1981 requires conduct 'more than merely preparatory'; conspiracy under the Criminal Law Act 1977 requires agreement to commit an offence; the Serious Crime Act 2007 creates three tiers of encouragement/assistance offences; and the Accessories and Abettors Act 1861 makes those who aid, abet, counsel or procure liable as principals. The rationale is preventing harm by intervening before completion and ensuring all culpable participants face liability—extending criminal law's reach both temporally (before the offence) and laterally (beyond the principal).

R v Geddes [1996] Crim LR 894: Lord Bingham CJ articulated the modern 'more than merely preparatory' test for attempts. Essential for understanding when preparation crosses into criminal territory. R v Jogee [2016] UKSC 8: Supreme Court overruled Chan Wing-Siu/Powell and English joint enterprise doctrine—accessorial liability requires intention, not mere foresight. Fundamental correction affecting thousands of convictions. R v Saik [2006] UKHL 18: Conspiracy requires the mental element of the substantive offence, not just intention to agree. Clarifies that conspiracy mens rea tracks the target offence. R v Shivpuri [1987] AC 1: Lord Bridge held impossibility is no defence to attempts, overruling Anderton v Ryan. Ensures attempts doctrine catches all preparatory conduct regardless of factual possibility. R v Tyrrell [1894] 1 QB 710: Established the Tyrrell exception—victims cannot be accessories to offences designed for their protection. Limits accessorial liability's scope.

Courts apply a sequential analysis. For attempts: (1) identify the substantive offence; (2) assess whether defendant's acts were 'more than merely preparatory'—fact-specific inquiry focusing on proximity to completion; (3) confirm mens rea matches substantive offence (but intent required for results—Whybrow for murder). For conspiracy: establish agreement between two or more persons to commit an offence, with mens rea matching the substantive offence. For accessorial liability post-Jogee: identify the principal's offence, then establish defendant aided/abetted/counselled/procured with intention (not mere foresight) that the offence be committed. Common triggers include interrupted crimes (attempts), criminal planning (conspiracy), and group offending (accessorial liability). The Tyrrell exception blocks liability where defendant is the protected victim.

Five critical errors: (1) Applying the old proximate-act test instead of 'more than merely preparatory' under the 1981 Act. (2) Using pre-Jogee foresight test for accessories—post-2016 requires intention. (3) Conflating accessorial liability with conspiracy—accessories participate in completed offences, conspirators agree to future offences. (4) Missing that impossibility is no defence after Shivpuri. (5) Forgetting the Tyrrell exception protects victim-defendants from accessorial liability.