When I was a law student studying criminal law, one concept that frequently eluded me was the defence of duress by threats. In my own rough and inelegant way, I learnt that the defence of duress by threats meant that you had a defence to a criminal offence if you could show that you carried out the offence because someone else had threatened to do something nasty to you, or someone you cared about, if you did not. Oh, and you couldn’t rely on the defence on a charge of murder. Or treason..
Duress was almost certainly an area I avoided at all costs when I sat my exams. So, it is heartening to know that even the courts will avoid answering questions about duress in any definitive way so long as they can help it. Indeed, even the big red bible of criminal law, Archbold, concedes that a “definitive statement of the scope of the defence is not to be found in the authorities.”
However, on Tuesday the Court of Appeal (Criminal Division) dipped its toe into the murky waters of the scope of duress in a handed down judgment is Regina v Dao and others  EWCA Crim 1717, although Lord Justice Gross, giving the judgment of the court, was at pains to make clear that his remarks on the matter were purely “provision”.
To the facts of the case. The three appellants, N, M and D, who were all Vietnamese and unable to speak English, were each convicted of cultivating cannabis. In late October 2010, the police forced entry into a set of premises in E17 in which they found the three appellants and a fully functioning cannabis factory. Each of the appellants were found to have fairly large sums of cash in their pockets.
The prosecution contented that the three of them had been caught red-handed. However, the defence case was that each of the appellants had been duped into entering the premises, under the pretence that they were there to clean it, and that once they realised what had happened they wanted to leave, but were threatened and locked inside with no means of escape. The nasty question of law this raised was whether the defence of duress should extend to false imprisonment. The reason this is such a difficult question is because the law has always been reasonably clear that there must have been a threat of death or really serious harm. It was less clear about whether being threatened with being falsely imprisoned alone was enough.
Fortunately for the Court of Appeal, this appeal could be dealt with without needing to enter into an examination of duress, because in the court’s view the evidence against each of the appellants was so overwhelming that their convictions were safe at any rate. However, Gross LJ did venture a “provisional” view on the matter. His Lordship’s provisional view was that he was “strongly disinclined to accept that a threat of false imprisonment suffices for the defence of duress, without an accompanying threat of death or serious injury” and that “any such widening of the defence… [was] ill-advised”. He based his reasons for that disinclination of the balance of existing case law and upon, what lawyers might call, “policy considerations”.
The starting point was the classic duress case of DPP v Lynch  AC 653, 686 in which Lord Simon defined duress as:
…such well-grounded fear, produced by threats, of death or grievous bodily harm [or unjustified imprisonment] if a certain act is not done, as overbears the actor’s wish not to preform the act, and is effective, at the time of the act, in constraining him to perform it.
But, Lord Simon added an important caveat, also at p 686
I am quite uncertain whether the words which I have put in square brackets should be included in any such definition.
The uncertainty over the issue of whether false imprisonment alone could be sufficient to ground a defence of duress persisted, mainly because of a dearth of cases that would allow the courts to deal with the issue head on – any statements of law on the matter were obiter (or, made “by the way”). However, Lord Justice Gross’ view of the law, namely that the defence was not available on a threat of false imprisonment alone, finds support in two fairly recent decisions. The first is Lord Justice Rose’s judgment in R v Abdul-Hassain  EWCA Crim 3528, in which he said that “imminent peril of death or serious injury” were essential elements of duress. The second is the decision of the late Lord Bingham in R v Z  UKHL 22;  2 AC 467. Lord Bingham made the point that duress operates so as to excuse conduct that is otherwise criminal and is extremely difficult for the prosecution to investigate and disprove. For that reason, it was necessary to “confine the defence of duress within narrowly defined limits…” and that “to found a plea of duress the threat relied on must be to cause death or serious injury”. So, no mention of being falsely imprisoned in a cannabis factory there either.
Gross LJ, having decided that the law offered no room for pleading duress in false imprisonment cases, then went on to bolster his view with the policy reasons against extending the defence, of which there were three main strands. The first was based on what Lord Bingham said in Z – once the defence is raised, it is for the prosecution to disprove it beyond reasonable doubt. To extend the scope of the defence would overburden the prosecution. The second strand was based on the cautionary words of Lord Simon in the Lynch case – “’your Lordships should hesitate long lest you may be inscribing a charter for terrorists, gang-leaders and terrorists”. The final strand seems to be that even though the defence is narrowly drawn, judges can still reflect the defendant’s relative guilt when sentencing.
As a matter of law then, the jury is still out as to whether false imprisonment alone can ground a plea of duress – the matter has been left open in the authorities, including this case. That is either beauty or the flaw of the common law.