Joseph McCann, who has been convicted of a horrific series of rapes and kidnappings against 11 women and children, was freed in error to commit his crimes after authorities failed to realise he should have been in jail for a previous violent offence.

McCann, 34, was found guilty on Friday at the Old Bailey of all 37 counts after attacking 11 women and children and could face a life sentence.

He raped eight victims, including an 11-year-old boy and a 71-year-old woman, during a fortnight-long rampage earlier this year that stretched from London to Cheshire. The boy aged 11 and his sister were attacked in front of each other in their own home.

After the unanimous jury verdicts, there were immediate calls for an inquiry into how McCann had been freed despite being subject to an imprisonment for public protection (IPP) sentence. This sentence, for a burglary armed with a knife in 2008, should have resulted in his recall to prison after a new conviction for burglary and theft in 2017.

Probation and parole experts said McCann’s mistaken release earlier this year came against the background of austerity-driven cuts to the justice system.

Joseph McCann case is about the system not the sentence Read more

The Ministry of Justice said the south-east and eastern division of the probation service was to blame for the error. That division has the highest workload in the service, according to a September report by the Inspectorate of Probation. Furthermore, “over half of the responsible officers” spoken to by inspectors revealed “their workloads were unmanageable”.

After an internal investigation, the MoJ said one staff member had been demoted.

The chief executive of HM Prisons and Probation Service, Jo Farrar, apologised for failings.

“We recognise that there were failings and we apologise unreservedly for our part in this. We are committed to doing everything we possibly can to learn from this terrible case,” she said.

Labour’s policing spokeswoman, Louise Haigh, said a “perfect storm” of cuts to the police, probation and judicial systems had led to McCann’s release.

Play Video 1:25 Dashcam footage shows police chase of car stolen by rapist Joseph McCann – video

The details of the error in McCann’s case follow the revelation that Usman Khan, the London Bridge attacker, appealed successfully against the length of his IPP sentence in 2013 and was then released without referral to the Parole Board, despite a judge saying the body should review his case before he was freed.

The judge in the McCann case, Mr Justice Edis, said he was considering a life sentence and would also seek an explanation of his licence conditions at the time of the offences.

The attacks took place over two weeks in April and May this year. McCann’s victims were taken off the street and subjected to barbaric ordeals.

The jury, which sat through harrowing evidence, issued a note after reaching their verdicts, praising the “bravery and courage” of the victims to come forward, and the hard work of the police.

McCann was not in the dock, having refused to attend his trial.

The court heard that a woman, aged 21, was taken from a London street in broad daylight while out with her sister. Her pleas to be spared were ignored, and McCann’s attack left her in physical agony. McCann told his first victim he had just got out of jail after “doing 18 years”.

The trial produced some of the most harrowing evidence heard in a British court in recent times. Jurors and members of the court were frequently upset by the distressing nature of the evidence, with the judge ending one day’s hearing early after a tape was played of a 999 call by a 17-year-old girl who was attacked in front of her brother.

Joseph McCann timeline Joseph McCann timeline

McCann’s first attack took place in Watford on 21 April when he snatched a 21-year-old woman at knifepoint on the street as she walked home from a club.

It was days before that attack was linked to two others in east and north London: on 25 April, a woman, aged 25, was dragged into a car in east London, imprisoned and repeatedly attacked in a 14-hour ordeal of “shocking depravity and violence”, the prosecutor, John Price QC, told the court. With her still in the car, McCann abducted a 21-year-old woman in north London, who was also repeatedly attacked and threatened.

He took the two women to Watford before their abduction ended when one smashed a vodka bottle over McCann’s head and passing builders helped them escape.

McCann lay low as a police manhunt tried to capture him over the next 10 days.

On 5 May, having met a woman in the north-west of England while out drinking, he tricked his way back to her home, waited for others to leave then tied her up. He then raped her 11-year-old son and 17-year-old daughter next door. The family’s ordeal only ended after the girl leaped out a window and ran to a neighbour’s house to call the police.

Hours later, still in the north-west, he abducted and raped a woman, aged 71, and then abducted and sexually assaulted a 13-year-old girl while the woman was still his prisoner.

That evening they escaped and McCann headed to Congleton, Cheshire, and abducted two 14-year-old girls. He fled after crashing the car, leaving the girls unharmed.

McCann was eventually captured early in the morning of 6 May in fields near Congleton, after being surrounded by officers, and climbing a tree to try to avoid them.

He taunted officers by saying: “If you had caught me for the first two, the rest of this wouldn’t have happened.” He was tied to crime scenes via DNA.

In May, when McCann was still at large, having started his attacks, the MoJ claimed a proper risk assessment would have been done before his release. That turned out not to be the case.

McCann had an extensive criminal history. In 2008, he was convicted of aggravated burglary after breaking into the house of an 85-year-old man and threatening him with a knife, demanding money.

He received an IPP sentence with a minimum tariff of two and a half years. The Parole Board decided he was safe to release in March 2017, on a 10-year licence.

In August 2017, he was arrested for burglary and theft, and sentenced to three and a half years in prison. The halfway point of his sentence was reached in February 2019, and he was released automatically.

Under the terms of his licence for the 2008 conviction, McCann should have been returned to prison, the MoJ accepted after an internal inquiry. The department said the inquiry report has been made available to McCann’s victims but it was not its practice to publish it.

Facebook Twitter Pinterest Joseph McCann after being caught by police. Photograph: Metropolitan police

McCann’s past offending, while extensive, was much less severe than the string of rapes for which he was convicted. He had in the past been convicted of affray for hitting someone in the face and also possession of a knife.

Harry Fletcher, the former assistant general secretary of the probation officers’ union Napo, said cuts imposed by the government on the prisons and probation service since 2010 might have been a factor in the mistaken release of McCann.

“There is a much greater chance of errors being made than ever before,” he said. “The background to this is that the budgets of both the probation service and prisons have systematically been cut over the last decade, so there is less staff and those that do remain have bigger caseloads.

“A recent parliamentary answer shows that one person a week is let out wrongly. There has never been a consequence as devastating as this.”

Nick Hardwick, the former inspector of prisons and former chair of the Parole Board, called for an inquiry.

“When the system is under so much pressure, that’s the sort of circumstances where mistakes are going to be made,” he said. “We need to be careful about assuming it was an individual [error] rather than it being a systemic failure.

“The probation service is in chaos and people are struggling with workloads.”

The charges were 10 counts of false imprisonment, seven counts of rape, one count of raping a child, two counts of causing or inciting a person to engage in sexual activity without consent, seven counts of kidnap, one count of attempted kidnap, three counts of causing or inciting a child under 13 to engage in sexual activity, three counts of assault by penetration, one count of sexual assault, and two counts of committing a sexual offence with intent.

McCann will be sentenced on Monday.