As the director of public prosecutions in charge of the Crown Prosecution Service, Alison Saunders has been branded toxic, disastrous and “the worst DPP in living history”.

Her five-year-tenure has been marked by repeated scandal, first with the £30m collapse of Operation Elveden – in which 34 journalists were arrested in an investigation into inappropriate payments to police officers, but no convictions were upheld – then with a series of collapsed rape trials.

On her watch, the crisis over the disclosure of evidence in rape cases – under which the police and the CPS have a duty to share information that may assist the defence case – led to hundreds being dropped.

An urgent review of all live rape cases was then conducted and crucial new guidelines on disclosure were drafted.

The press called for the DPP’s resignation and MPs criticised her ability to handle the job. It is fair to say that Saunders has endured a tricky time.

“I never thought I would be in a position to be offered [this job], or that I could even apply for it,” she says quietly. “I didn’t join the CPS thinking I wanted to be director – I wasn’t whooping when I knew Keir [Starmer] was leaving.” After 32 years in the department and as the first DPP to be appointed from in-house, Saunders is leaving to join law firm Linklaters next month.

“[This was] the absolute pinnacle and, I think, not just for me but for the service,” she says. “We’d been used to people being jetted in, the perception was that you needed outside leadership.”

Saunders thinks she has done a good job: “I do, I do. [It’s] been quite affirming internally, saying goodbye. People think I’ve done a good job – it matters what people in the service think.” She is proud, she says, of changing the work culture where there is “smarter working, so we have people working remotely and from home” and of reportedly boosting staff morale while presiding over 25% funding cuts and shedding a third of the now 6,000-employee workforce.

But the focus on internal working procedures is a curious one for Saunders. Under her leadership, significant strides have also been made on modern slavery and human trafficking cases, on violence against women and girls, on the national understanding of coercive control and in the training of police and prosecutors to deal with victims of rape and serious sexual offences. The number of rapes reported to the police, meanwhile, jumped from some 16,000 in 2013 to 40,000 in 2016.

At the same time, the conviction rate for rape in the UK stands at 6.5% – the lowest of 33 European countries – and the police now routinely mine data from social media accounts, local health authorities, phones, laptops and the like from claimants. The notion of a legal “digital short skirt” has emerged, in which much of this information can be used to undermine a victim in court and uphold rape myths. “It’s about prosecutors dealing with what we’ve got and this huge attrition rate between a report being made and it then coming to us for referral – that gap is widening and we need to work out why.”

The CPS is yet to get to grips with many of the problems that Saunders agrees it faces, but she is scathing about “the lack of resourcing”, and the inability of the police to cope with the swell of technology and data associated with modern crime is her primary concern. Is the criminal justice system failing? “It’s really creaking. Take one recent rape case where they met on Tinder – it took 600 police hours to go through the digital material.”

She admits that the massive upward tick in fraud, for instance, is almost being ignored “because it takes time and a skilled investigator”, of which the system is in dire short supply. “You can have a judge say ‘I want a download of that iPad’ and it will take 15 officers working all weekend to get it.” The technical knowledge required to combat modern crime is, she says, overwhelming.

“Think about it – when we first got the legislation for disclosure in 1996, only 16% of houses had a mobile telephone. It is a huge challenge for the police and the whole system going forward. It needs an investment of resources nationally, in capacity of forces and in future-proofing it. Who is making the plans for what’s going to happen in five years?”

Some cases, she says, can end up “with downloads taking six to eight months” in which suspects, witnesses and victims are left hanging during the investigation. Despite facing that pressure, Saunders denies she enforced a culture of conviction targets.

“It would be quite wrong to do that,” she says emphatically. “An acquittal, for example, is not a disaster – it’s the system working because we are not judge and jury and nor should we ever be. What we do is apply a test: is there a reasonable prospect of conviction?”

The central function of the CPS, she says, “is to make sure we prosecute the right person for the right charges and decide whether we think a case should go to court. It’s not our function to decide if someone is guilty”.

She is “frustrated” at being unable to “get that message across”. But Saunders is bruised by her experience. “Sometimes we will mistakes, and humans do,” she says. How has she personally managed with the low points? “Undoubtedly, some of the personal accusations – which I don’t think are founded – how do I manage with those …”

Saunders’s voice breaks and she begins to cry. “This is really stupid,” she waves, frustrated. She pauses and sighs to compose herself.

“It’s when you get those messages of support, when it’s from people in the service but also those outside who have taken the trouble to write and to say ‘that was good’”. Her voice wobbles. “When they say ‘we agree with you’.” Saunders pauses again, holds her breath and gently dabs her eyes. “It has been challenging but it’s also a real privilege to lead this organisation.”

Saunders insists she hasn’t been hounded out of the job, but says that she told the attorney general last December that she would not be applying for an extension of her contract. The news that she quit was leaked to the press in April.

“I don’t think you’d be human if it didn’t affect you,” she says. “I can cope. I have great family and friends that can support, but what is difficult to cope with is on behalf of the service itself and the people who work here.” Her voice trembles again.

“You can have one really awful story on the front page and then you have four fantastic stories inside that don’t get recognised.”

She pauses again. “I don’t understand where some of the rhetoric comes from ... but I think five years [in this job] is long enough for anyone.”