Should a legal plea of self- or third-party defence include an 'awareness component' that requires that the actor was aware of the so called justificatory facts at the time of action? Some theorists argue that in cases of so called unknown defence, where an actor in fact averts an otherwise unavoidable danger to himself or another person although unaware at the time of action that this is what s/he is doing, the objective facts alone should allow a justification defence such as self-defence. Cases of unknown defence raise issues that are highly significant to the nature of justification and liability. In this paper I reject some common approaches to this issue, and I offer an account of why cases of unknown defence are appropriately subject to criminal liability for the complete offence (e.g., murder).