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criminal law defences

if mistake is used as a defence, does this exclude liability completely?
Reply 1
Mistake is not a defence in its own right. I'm not sure if you're talking about what I'd call actual defences, such as self defence, necessity, duress etc. or if you are talking about an element of a particular offence, for example the defendant's lack of (reasonable) belief in consent in rape, where the defendant could say he mistakenly (but reasonably) believed there was consent when in fact there was not. I wouldn't call that a defence though, that is simply where the prosecution do not prove the elements of the case. A defence, as I see it, is where the prosecution do prove the elements of the case but there is something extra the defendant raises which can, if you like, trump what the prosecution have proved.

So for example the prosecution might have proved all the elements of GBH, and then you can argue self defence, and say that you had a mistaken belief someone was going to attack you. In that case provided your force is reasonable and your mistake was an honest one, then yes that will exclude liability. Generally a mistaken belief giving rise to a defence need only be honest - I am unsure if there are any examples where it needs to be reasonable. Certainly though, in the field of sexual crimes, where an element of the crime is a belief in something very often that belief has to be a reasonable one, and sometimes even a reasonable one will not suffice, such as where the defendant mistakenly believes the victim is over 16 when they are in fact under 13, when charged with child rape.

So, in summary, you need to differentiate between:

1. mistakes giving rise to legal defences such as a mistaken belief of the need to defend yourself, which generally need only be honest and will exclude liability.
2. mistakes regarding an element of a crime which requires the defendant's belief in a particular state of affairs, such as the consent of the victim or their age, which generally need only be honest to exclude liability but in the case of sex crimes often needs to be reasonable to do so. And remember with some strict liability offences such as child rape even a reasonable mistake about the age of the victim will never exclude liability.
(edited 12 years ago)

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