A first hearing in the case of Lord Janner is due to take place.
An independent review overturned the original ruling of Director of Public Prosecutions (DPP) Alison Saunders that the former Labour peer should not be charged for alleged child sex crimes because he is suffering from Alzheimer's.
A trial of the facts, where a jury hears the evidence against an individual considered too ill for a full trial, is expected to be held into the 22 offences allegedly committed in the 1960s, 1970s and 1980s.
The case is listed for a first hearing at Westminster Magistrates' Court.
Ms Saunders' enforced U-turn, announced in June, led to calls for her to resign.
Simon Danczuk, the Labour MP for Rochdale who has campaigned for the case to be heard in court, said then that Ms Saunders was responsible for a ''catalogue of errors''.
He said: ''I think she should resign for an number of reasons. She has made a number of bad judgments and she is just not fit to do the job.
''She made mistakes on a case around FGM (female genital mutilation), serious errors in her attempt to prosecute journalists and now another serious error regarding the Lord Janner case.
''She ignored her advisers, took a long time to make the decision, then announced it when Parliament was not sitting although there was significant public interest.
''Most important of all, it was a serious mistake because she failed to understand both the mood of the public and the emotional distress she was causing to the alleged victims.
''We cannot have somebody leading the Crown Prosecution Service (CPS) who is cold and dispassionate towards alleged victims.''
The 87-year-old peer's family strongly denies claims he used his power as an MP for Leicester to abuse vulnerable young boys at a local children's home.
A judge will have to decide if Lord Janner is fit to plead. If he is not, a jury will be asked to decide whether he did the acts he is charged with.
The judge will also have to rule on whether the defendant should appear during the trial or can be excused on medical grounds.
A trial of the facts is not considered a trial as such because the defendant cannot put forward a defence.
There is therefore no guilty verdict and the court cannot pass sentence.
All it can do is make a hospital order, a supervision order, or an order for the defendant's absolute discharge.
Ms Saunders's decision in April not to charge Lord Janner was reviewed after six of the complainants made a request under a scheme introduced two years ago giving victims the right to challenge CPS decisions.
She is the first DPP to have a major prosecuting decision reviewed and overturned through the new policy.
An independent inquiry into child sex abuse being led by Justice Lowell Goddard is also due to hear evidence from the complainants.
Ms Saunders said in June: ''I don't think in any way it's a resigning matter.
''It shows the process we have implemented works, it shows we will look at victims' right to review and overturn decisions when we decide that's the right thing to do.
''Certainly over the last 18 months there is nothing else there that says I should be resigning, so I won't be.''