R v Shepherd (1988) 86 Cr App R 47
The availability of the defence of duress where the defendant initially voluntarily engages in the relevant criminal activity.
The defendant entered a shop with a view to stealing boxes of goods from it. When charged with burglary, the defendant raised the defence of duress on the basis that whilst he had willingly participated in the crime initially, he subsequently lost his nerve. However, the defendant stated that he felt compelled to continue to contribute to the burglary because he and his family had been threatened by violence by one of the other participating parties.
At first instance, it was held that the defence of duress was not available on these facts because the defendant had voluntarily participated in the criminal act. The issue for the Court of Appeal was whether the subsequent change of mind was sufficient to allow the defence to be raised at that stage.
The defence of duress is available where threats of violence to the defendant or those close to the defendant exist to such an extent that the defendant feels compelled to contribute to the crime and it would therefore, be unjust to find them criminally liable for their actions (DPP for Northern Ireland v Lynch  AC 653). It was held here, that the defence would be available following voluntary involvement in criminal activity if, at the time of the voluntary involvement, violence was not contemplated. Once the defendant changes their mind and wishes to cease involvement, the defence will be available if, at that stage, they are aware of the threat of violence. In other words, the defence will not apply where there is a threat of violence initially, but at this stage the defendant voluntarily contributes and later changes their mind.