Question: Can you define what is reasonable doubt? Answer: A reasonable doubt is a doubt that is reasonable. These are ordinary English words.
Not all the ten questions put by the jury to the judge in the trial of Vicky Pryce, the former wife of the LibDem MP Chris Huhne, were as elementary as this one but most needed no expert answer. Common sense would have been enough.
For instance: Can a jury come to a verdict based on a reason not presented in court and which has no facts or evidence to support it? No, no, no.
Perhaps Mr Justice Sweeney need not have referred so blatantly to the jury's fundamental deficit in understanding but he was obviously right to dismiss its eight women and four men and order a retrial with a new jury.
Ms Pryce is accused of perverting the course of justice by taking her husband's speeding points in 2003.
As usual when a jury fails to reach a decision there is criticism of the system but when that occurs it is invariably a human failure -- an obstinate member or a collective inability to deal with unfamiliar and complex issues.
On the whole the system works and those judged can feel that it has been by their fellow citizens. What happens in the jury room is sometimes a mystery but it must remain that way.