The Crown Prosecution Service is due to announce on 29 June that Lord Janner will face a "trial of the facts" in connection with allegations of historic child sexual abuse following a review by an unnamed QC.

This would overturn a decision in April by Alison Saunders, the Director of Prosecutions, not to charge the 86-year-old Labour peer due to his dementia, meaning he was unfit to enter a plea. She also cited public interest concerns.

In a "trial of that facts", a defendant cannot enter a plea, and therefore cannot be found guilty of any crime. He or she will be represented by a lawyer who will put his or her case forward. At the end of the trial, the court will issue a hospital order, a supervision order or an order for the defendant's absolute discharge.

The Guardian reports that this is possibly the first time that alleged victims have succeeded in overturning a DPP's decision.

The decision to overrule Saunder's decision will put her under pressure to resign.

One, anonymous, alleged victim told the paper: "It shouldn't have taken this long – 45 years for some – to get to this point. Saunders should go because she has tried to stop the truth from coming out."

Another alleged victim, Paul Miller, 53, told the Sunday Express: "It's great news but Alison Saunders should be sacked. She's been proved to be incompetent in not making the right decision in the first place. Her position is now untenable."

Miller has claimed that he was groped by the peer, a former president of the Board of Deputies of British Jews, during a school visit to Westminster when he was nine.

Pressure is also mounting in parliament for Saunders to step down.

As previously reported in IBTimes UK, Rochdale Labour MP Simon Danczuk said on 26 June: "All suggestions are that Saunders reached the wrong conclusion in April and this is not the first time she has made a major mistake. She has struggled in some of her decisions to pursue journalists through the courts, too. Her job is all about judgment."

David Davis, the Conservative MP and former shadow home secretary, said: "It is hard to know why she decided not to have a trial of the facts in the first place, only to decide to do so after the huge political furore. This has been a terrible process which has prolonged the misery not just for the alleged victims but also for Janner and his family."

Liz Dux, a lawyer from Slater and Gordon representing many of the alleged victims, told The Guardian: "My clients are delighted by this decision. It is a total vindication of why they challenged the original decision of the DPP. All they have ever wanted was to give their evidence in a court and have findings of fact established. They have been denied this right for many many years but now their faith in British justice is restored and they look forward to being listened to after so long."