Victims of serious crime now wait almost a year-and-a-half for the suspects to go on trial while judges sit “idle” after the government cut their sitting days – despite Guardian analysis finding almost half of all crown courtrooms in England and Wales are empty each day.

Government statistics show that the average crown court case takes 525 days to go from offence to completion, up 34% from 392 days in 2010.

The delay begins with the police, who have had their numbers cut by 20,600 since 2010. Ministry of Justice (MoJ) statistics show that overwhelmed forces now take an average of 331 days from the date of the offence to charge someone with a crime that will see them tried at a crown court, up from 205 days in 2010.

The suspects then wait longer for their cases to be tried in court because the government has been reducing the number of sitting days for crown court judges as part of cost-cutting measures at the MoJ. Allocations fell from 97,400 in 2018-19 to 82,300 in 2019-20, according to the senior presiding judge, Lady Justice Macur. Judges are still paid the same annual salary but find themselves idle behind the scenes, unable to hear the mountain of cases piling up.

The Guardian analysed the listings for all crown courts in England and Wales on one day in December and found that of the 729 available courtrooms showing on the government’s Xhibit system, which relays hearing information, 350 were not sitting.

In St Albans crown court in December, one “extremely serious” historic sex case was postponed for six months because of a lack of court sitting days, leaving both the complainants and the defendant in “a dreadful state”, according to Caroline Goodwin QC, chair of the Criminal Bar Association (CBA).

“They only found out on the Friday before the Monday trial that the case was not being listed,” she said in her weekly roundup. “The defendant was elderly. The list office said there would be a six-month delay before the new trial date. The local head of the Crown Prosecution Service rape and serious sexual offence unit became involved as the complainants were exceptionally distressed and unable to support such a long delay.”

One crown court judge expressed frustration with the cost-cutting: “There is a simple solution. These cases need judges. This is not rocket science. There are significant numbers of fully trained, part-time criminal judges who are ready, willing and able to help out, yet they are sitting idle whilst the criminal justice system suffers delay after delay.”

They added said: “The judges, the buildings, the staff are all there but there will be no solution to this problem until Government fund the system properly. Justice delayed is justice denied. ”

On 16 December, 10 out of 21 courtrooms at Snaresbrook crown court in east London were not sitting; at the central criminal court, also known as the Old Bailey, 10 out of 22 were empty. Reading crown court was the only one of 84 crown courts in England and Wales to use all of its available courtrooms that day.

Snaresbrook is likely to become further overwhelmed when Blackfriars crown court closes on 20 December, sold by the government for an estimated £32m. “What is Snaresbrook going to do with the 300 extra cases it receives once Blackfriars closes and its work is redirected there?” said Goodwin in her roundup. “Resident judges must dread having a hung jury. Just when can they relist those trials? From information passed to the CBA, if such a situation were to occur at Southwark, it is likely the new date for trial would be mid-2021-22. We need more sitting days.”

Some cases are taking so long to reach trial that suspects on remand have to be released from jail because the custody time limit has been reached, posing a potential danger to the public.

The lack of available court time can have a serious effect on vulnerable victims.

In Leeds crown court at the end of October, another rape trial involving an elderly complainant with dementia collapsed after several days of problems playing video interviews in court. The jury was discharged and the first date the court could find to hear the case again was in May 2020, almost two years after the alleged rape took place.

The complainant’s niece said the delay was devastating for her and the family. She said: “The stress this has placed on my aunt is catastrophic with all the emotional psyching up required each time the trial is scheduled. She is physically disabled and extremely frail. She also has dementia, which is known to be accelerated by stress and her rapid deterioration has been marked over the course of these events. Not to mention the family and everyone else involved in the case.”

A spokeswoman for Her Majesty’s Courts and Tribunals Service said the technology problem at Leeds crown court was a one-off and apologised to the complainant for the distress caused.

The Ministry of Justice said: “The number of outstanding cases at the crown court has decreased by almost 40% since 2014 with waiting times for these cases at their lowest ever.

“We keep sitting days under constant review and allocated an extra 700 crown court sitting days for the remainder of 2019/20 in response to an increase in cases coming to court.”