Defence of Drunkenness in UK Law

What then is the mental element required in our law to be established in assault? This question has been most helpfully answered in the speech of Lord Simon of Glaisdale in R v Morgan [l975] 2 W.L.R. 913 at page 939:

If a man of his own volition takes a substance which causes him to cast off the restraints of reason and conscience, no wrong is done to him by holding him answerable criminally for any injury he may do while in that condition. His course of conduct in reducing himself by drugs and drink to that condition in my view supplies the evidence of mens rea, of guilty mind certainly sufficient for crimes of basic intent.

In the case of these offences it is no excuse in law that, because of drink or drugs which the accused himself had taken knowingly and willingly, he had deprived himself of the ability to exercise self-control, to realise the possible consequences of what he was doing, or even to be conscious that he was doing it. As in the instant case, the jury may be properly instructed that they "can ignore the subject of drink or drugs as being in any way a "defence" to charges of this character.

The ordinary citizen who is badly beaten up would rightly think little of the criminal law as an effective protection if, because his attacker had deprived himself of ability to know what he was doing by getting himself drunk or going on a trip with drugs, the attacker is to be held innocent of any crime in the assault.

Indeed, in cases where drunkenness and its possible effect upon the defendant's mens rea is an issue, we think that the proper direction to a jury is, first, to warn them that the mere fact that the defendant's mind was affected by drink so that he acted in a way in which he would not have done had he been sober does not assist him at all, provided that the necessary intention was there.

Secondly, and subject to this, the jury should merely be instructed to have regard to all the evidence, including that relating to drink, to draw such inferences as they think proper from the evidence, and on that basis to ask themselves whether they feel sure that at the material time the defendant had the requisite intent.

if (1) he does an act which in fact creates an obvious risk that property will be destroyed or damaged and (2) when he does the act he either has not given any thought to the possibility of there being any such risk or has recognised that there was some risk involved and has nonetheless gone on to do it. That would be a proper direction to the jury; cases in the Court of Appeal which held otherwise should be regarded as overruled.