A defendant who commits a crime under duress may in certain circumstances be excused liability. The defence can arise where the duress results from threats or the circumstances in which you find yourself.
The four elements of duress are as follows:
That you reasonably believed that threats of death or serious injury had been made against you.
That you reasonably believed that the threats would be carried out immediately and the threat was effective in the sense that there was no reasonable avenue of escape open to you to avoid the perceived threat
That the threat of death or serious injury was the direct cause of you committing the offence.
A sober person of reasonable firmness of your age, sex and character would have done what you did.
The prosecution must prove your guilt. It is for them to prove that the defence of duress does not apply. It is not for you to prove that it does apply.
There are several authorities regarding drink driving and duress. Some of which are outlined in brief below:
DPP v Jones  RTR 33
The defendant had been subjected to an attack in the car park of a public house. He got into his car which was then hit and kicked. He decided his only means of escape was to drive away. He continued to his home, a distance of one-and-a-half to two miles. The court held that the defence of necessity was available for a part of the journey to his house. The defendant did not even bother to check whether he was being pursued, whether on foot, or in a vehicle or in any other way. The defence of necessity did not avail the defendant other than for the initial part of the journey. It was unnecessary for him to have continued all the way home in his car. He could easily, especially as it appears that he was not being pursued, have pulled into a side road or into some other convenient place and proceeded for the rest of his journey home on foot. The defence of duress was not available to the defendant because he drove for a longer period than was necessary.
DPP v Bell  Crim. L.R. 176
The defendant had been out drinking with some friends. Some trouble broke out which caused him to run back to his car pursued by others who were less than well disposed towards him. Fearing serious physical injury, he drove off for some distance in a state of terror. The fact that he drove only for some distance down the road and not all the way home was of significance. The defence of duress applied and had not been disproved by the prosecution.
DPP v Pittaway  Crim. L.R. 600
The defendant ran 200yds home from a party outside which she had been the subject of angry words and unspecified threats from a man with whom she had formed a relationship, hid in her car for five minutes and then drove 200yds before being stopped. The man she was seeking to avoid was not in the vicinity at the time. In the court’s view, the justices had neglected to apply the objective limb of the test, since there was no evidence in either case of a threat of death or serious bodily injury.
DPP v Tomkinson  R.T.R. 38
Following a New Year’s Eve party, the defendant was violently assaulted by her husband, who also injured himself and then departed in a taxi for hospital having left her without a phone, but saying that police were on their way and that she had better leave before he returned home. The police having failed to arrive, she left her house at about 6am to drive to her former home (where her children were) some 72 miles away. She was stopped by police about 9.30am and when breathalysed was found to be over the prescribed limit. The defence of duress did not avail her; she was no longer subjected to any effective threat of violence when she left the immediate area of her home in her car to commence the long journey from Harrogate to Sale, and there was no basis for the justices’ conclusion that a sober woman of reasonable firmness would or might have responded to the situation as the defendant did and drive 72 miles over the Pennines
Mr Brown said that he had driven to avoid a violent confrontation following a threatening phone call. At the time he was stopped there was no evidence that the threat was continuing or that he reasonably believed he was being pursued. The case was remitted to the magistrates’ court with a direction to convict. The court did not have to resolve the question of whether or not the defence was available at the time he got into the car as it was not available when he was stopped.