By Ben Ando
BBC crime reporter
For nearly 800 years the principle of the jury - that the guilt of anyone accused of a crime should be decided by a panel of their peers - has been the foundation of British justice.
In the film 12 Angry Men, one man persuaded fellow jurors to acquit
However, the BBC has learned that in the last two years the number of hung juries - where no verdict is reached - has more than doubled.
Figures obtained from Her Majesty's Courts Service under a Freedom of Information request show that in 2006 there were 52 hung juries in England and Wales. In 2007, that figure had risen by a third to 68.
Yet last year, there were 116 hung juries - an increase of 70 per cent, and more than double the figure just two years previously.
Jurist Trevor Grove - author of The Juryman's Tale, one of the few books to lift the lid on the secretive world of the jury-room - believes changes in society are being reflected.
"I do think that we live in an era when people are much more nervous about being judgmental," he said.
"In fact, judgmental is used as a pejorative adjective more often than not whereas the generation before mine, and certainly the generation before my parents', were quite happy to be judgmental."
A hung jury is bad for everyone; the defendant faces ongoing uncertainty, witnesses may have to give traumatic evidence again and the taxpayer will have to pay for any possible retrial.
The number of juries that are hung is still only a tiny fraction of the total. Even in 2008, the year in which there was a sudden surge, hung juries represented only 116 cases out of a total of 16,718 that came to court, or just 0.7 per cent.
Even so, with the broadly accepted figure of a crown court trial costing up to £80,000 per day, this still means that hung juries cost the taxpayer nearly £30m last year - and that does not include the cost of any retrial.
Queens Counsel Paul Mendelle, vice-chairman of the Criminal Bar Association, is worried about over-reaction to a statistical anomaly.
"Of course it's unsatisfactory. It's always unsatisfactory when decisions aren't arrived at when the purpose of the proceedings is to arrive at a decision," he said.
"But one doesn't know why these juries are hung; one doesn't know the causes and this is not statistically significant - it's less than a per cent - so it's not in my view a significant problem that requires addressing."
It is almost impossible to carry out research into why juries reach their verdicts in the way they do. Strict contempt of court legislation makes it an offence for jurors, after a trial, to talk about what took place in the privacy of the jury room.
Nonetheless, Trevor Grove believes that one reason for indecisiveness is the so-called CSI effect - that forensic evidence is now dominating trials.
"The great breakthrough here is DNA - I mean especially in a case like a murder. They (the jury) would like to see the prosecution having all the boxes ticked," he said.
"But, the fact is, if it were that clear cut the case probably wouldn't have come to trial; the defendant would have been advised to admit his guilt. Cases are very seldom that clear cut - that's why they go for trial."
Although formal research on jury deliberations is almost impossible, notes sent by juries to the judge during their deliberations can give a clue as to what they are thinking - and why they might be stuck.
A significant proportion of jury notes ask a similar question: "How sure do we have to be?"
The level of proof required for a defendant to be found guilty at a criminal trial used to be "beyond reasonable doubt," but judges tend to tell jurors they should be "certain so as you are sure".
This can lead to strong debate as to whether the scintilla of doubt afforded by the earlier phrase is now applicable; is it acceptable for a juror to convict if he or she is 99 per cent sure, or 95 per cent sure?
Trevor Grove believes most juries already work to this sort of level and said in his experience "juries do accept that about 95 per cent - pretty pretty sure - is good enough."
Judges can accept majority verdicts of at least 10 jurors if a unanimous decision is impossible. Reducing the majority from 10 to nine or eight is another idea that fills Paul Mendelle QC with dread.
He says he would be "wholly against any change which made juries less sure of guilt when people are facing serious crime, when they are at risk of losing their reputation, their livelihood or their liberty."
"It's not right that they should go to prison for anything less than certainty," he added.
It has been said that any tyrant assuming power would be obliged to abolish the jury system; the concentration camp or gulag can only be filled when there is incarceration without trial. Juries are - at their most fundamental level - democracy in action, in each court, every day.
And some argue that the hung jury, while unsatisfactory, is part of the normal running of the criminal justice system - in effect a rebuke to those charged with administering justice that they need to raise their game if they wish to secure either an acquittal or conviction.