Criminalising Unknown Defence

Prof Suzanne Uniacke (Charles Sturt University)

How should the criminal law respond to cases of so called unknown justification, and to instances of so called unknown defence in particular?  Such cases arise when an actor uses force against another person that can be justified on the objective facts, but these justificatory facts are unknown to the actor at the time of action.

Although such actions are rare,  they raise important issues of justification and liability.  The paper argues that some prominent approaches to assigning criminal liability for acts of ‘unknown defence’ are seriously flawed.  These approaches include the idea that criminal liability in such cases should be based on the actor’s moral blameworthiness, and the view that ‘unknowingly justified’ actors should be charged with the relevant attempted crime (e.g. attempted murder).  The paper maintains that in such cases the actor should be charged with the complete offence (e.g. murder) and denied a justificatory defence (e.g. self-defence). The argument for this view invokes the normative significance of the structure of justification defences such as self- or third-party defence.