By Hugh Levinson
There has been a huge jump in the proportion of defendants pleading guilty at trials in England and Wales, thanks to a new system of charging criminal suspects.
Traditionally, the police have had the job of charging suspects.
Now, prosecutors are taking over, in a new system which is gradually being rolled out across the country.
They will make decisions about which suspects to charge or release. The new system applies to serious offences which are likely to be contested.
At police stations like Harrow, in Middlesex, they are finding it a huge - and welcome - change.
"Prior to this we decided who was charged and with what offences and we would present the case to the Crown Prosecution Service," says Detective Sergeant Trisha Nurse.
"Now we bring the CPS in right at the early stages of the investigation, sometimes before even an arrest, so we can get our heads together."
CPS lawyers work in the station from 9 to 5. Out of hours, officers can phone a CPS direct advice line.
Local prosecutor Manjula Nayee says when she is brought into a case, she will often ask the police to take further action to strenghen the possibility of a conviction.
For example, in domestic violence cases - which are notoriously difficult to prosecute - she will often ask detectives to re-interview the victim.
"I would also ask the officer to investigate a previous history of domestic violence and giving full support to the victim in making sure that she comes to court and gives evidence."
It is a big cultural shift for many officers, and DS Nurse says many initially resisted the change. Now they're seeing the benefits.
Police have, she observes, traditionally been in the business of arresting "the bad guys" and charging them as soon as possible.
"Without a doubt we used to try and charge some people way too early," she says. "We had some evidence and we would charge them and send them to court and then we would, on a wing and a prayer, hope that the evidence would come in in time."
The CPS are claiming the results are highly successful - although their figures cannot directly compare like with like, due to changes in calculation systems.
Over the last two years, the ratio of defendants pleading guilty at magistrates courts has shot up from 40% to 66.8% in the areas operating the new system. In Crown Courts, the ratio has risen more modestly, from 61% to 65%.
There has also been a fall in the number of prosecutions being abandoned during the trial process.
"It takes time of course for all of this to bed in," says Ken Macdonald QC, who heads the CPS. "But all of the figures are moving in the right direction."
He denies that the new rules mean that due process is being whittled away for defendants or that prosecutors will end up in the pockets of the police. CPS lawyers will, he pledges, give "robust and independent" advice to officers.
But Mr Macdonald does believe that prosecutors could eventually end up joining police in their squad cars.
"There is virtually no limit to the help that prosecutors can give to investigators in the right circumstances," he says.
Law in Action is on BBC Radio 4 at 1600 GMT.