Alison Saunders of the Crown Prosecution Service talks about the Lawrence case and why a debate on rape is needed

Alison Saunders is probably the UK's most experienced criminal prosecutor. She has overseen the convictions of serial rapists and serial murderers ? and, in one particularly horrendous case, a man who was both.

Saunders says it "never ceases to amaze me what humans can do to each other, and how awful some humans can be".

But there has been only one occasion during her 26-year career when her work gave her a sleepless night.

It was just before the jury went out in the Stephen Lawrence trial at the Old Bailey this month. As head of the Crown Prosecution Service in London, it was her call to charge the defendants, Gary Dobson and David Norris, and her decision to go to the high court to seek a retrial under the double jeopardy laws.

During two years of complex legal midwifery, she got to know Doreen and Neville Lawrence, the parents of Stephen, and recognised their hopes were resting on her judgments.

"We knew that this might be our one and only chance," she said. "I was thinking ? are we going to get any more evidence in the future or is this the high point? Do we have all the material? Can we ensure there will be a fair trial?

"This was 18 years' worth of investigation. There was a lot riding on it ? we couldn't afford for it to go wrong."

It did not, and Saunders says she is relieved that Stephen's family "have got some justice".

But there is obviously frustration too. "When we were making the decision about Dobson and Norris, we didn't just look at them. We looked at what we had and whether there was enough to go against anyone else.

"Certainly with what we had at the time, there was not enough for a realistic prospect of conviction. Which is a shame because we know that other people were involved.

"If we get more evidence, then we will go against someone else. We haven't had anything referred to us since."

For now, she must put Lawrence to one side. A quarter of all crime in England and Wales occurs in the capital ? twice as much as anywhere else in the country. At the moment, she is looking forward to the Olympics and reflecting on London's riots.

And she is trying to spark a debate about rape and what can be done to encourage more victims to come forward. In a speech on Monday she will raise the uncomfortable and controversial issue of whether jurors are partly to blame for the difficulties prosecutors have securing convictions against suspected offenders.

In London, she has between 150 and 200 specialists looking at rape cases and has established a charging centre where 10 of her senior lawyers decide which of the 870 investigations referred to them will go forward to trial. At the moment, it is about half.

The CPS and the police have been criticised for failing to jail more rapists but Saunders believes the problem is not just one for investigators.

She argues a lot has been done to challenge and reform the way the authorities treat victims and suspects. "People don't understand how difficult it is for us not to proceed in a case," she said.

"What staggers me is when I remind myself that it was only in 1991 that the law was changed to make rape within marriage an offence. When you look at that then the developments in rape are all relatively recent."

She accepts the CPS is not getting it "entirely right", but she has been frustrated by how many rape trials end in acquittals and believes society is lagging behind the legal system when it comes to its view of women.

Saunders says she and colleagues have had to challenge any prejudices they had ? in particular assessing allegations made by young women who have been drinking, or those who accuse former partners.

But what about jurors?

"We have done a lot of work around myths and stereotypes," she said. "We have had consultant psychiatrists to talk to us about things like ? you cannot expect a rape victim to break down in tears, you cannot expect them to tell the story straight.

"You can see how some members of the jury can come along with preconceived ideas. They might still subscribe to the myths and stereotypes that we have all had a go at busting."

Judges advise jurors about what they should have in their minds when coming to a decision.

But this often comes towards the end of a trial ? too late to have an impact, Saunders says. But she does not think jury vetting is a realistic option either.

"Then it becomes debate about how much do you cross-examine a jury before they sit and what their morals and values are. And who makes a judgment on that?"

The debate has to start outside the courtroom, and may require some sort of government-led campaign, she argues.

Victims, she says, should go to one of the Havens ? clinics which give specialist care to sexually assaulted women. Even if they do not want to talk to the police straight away, they might change their minds later.

In one case, the CPS successfully prosecuted a man three years after the initial complaint.

"That's a very good example of how they work. If she had wanted to do it at the time, she was all over the place, and probably would not have been able to withstand it going through the system. She was able to make that choice later."

Born in Aberdeen, Saunders, 50, has been at the CPS since it was formed in 1986. "It doesn't pay nearly as much as my colleagues in contract and company law, but it was always crime for me," she said.

She had previously been advising underwriters at Lloyd's of London, but found it "a bit boring".

She also had two years as chief crown prosecutor in Sussex, where she oversaw the prosecution of Roy Whiting for the abduction and murder of the schoolgirl Sarah Payne.

One prosecution which had a profound effect on her was that of the "railway rapist" David Mulcahy, who was finally convicted in 2001 after his accomplice in murder and rape, John Duffy, testified against him. The crimes dated back to the 1980s and their victims included a 14-year-old girl.

When Duffy, already in jail, decided to give evidence, he was brought to court for a closed hearing so he could give a detailed chronology of what they had done.

"It was 17 rapes and three murders, and a whole progression, starting off with a night-time burglary through to really horrible murders. We were in Brent magistrates court. We were locked in and Duffy came in. When he started telling the story of such awful offending ? you could have heard a pin drop."

The grim task of going through cases like this has not taken a toll, she says, because she is "very good at compartmentalising. Most people who know me in my private life are amazed I do the job I do." But it has made life difficult for her two teenage sons. "I have become a very neurotic mother."