He assaulted them in the cells and interview rooms of Market Street police station in Newcastle city centre, knowing that if they complained they were unlikely to be believed.
One of them, a 19-year-old when he first struck, estimated she had been abused 100 times as he kept track of her using the police computer.
One victim was ‘disgusted’ at his release.
“He should have been locked up for life.” she said.
Out of total of 26 charges, he was convicted of two rapes, three indecent assaults and six offences of misconduct in public office.
During a five-week trial, in 2010, the prosecution said Mitchell preyed on heroin addicts, shoplifters and a disabled teenager by offering them help while in custody, then demanding sexual favours afterwards.
He had a hold over one woman for three-and-a-half years, even trying to keep her on heroin after she had quit, which only ended when she went into hiding after he raped her in handcuffs at her home, it was alleged.
The woman, now in her 30s, was locked in a patrol car and raped after she was arrested for theft.
Mitchell had promised the woman, who was addicted to heroin, he would help her regain custody of her children in return for favours.
Others were flattered then propositioned while still in custody with a view to beginning sexual relations later.
He paid one £20 for sex after arresting the 27-year-old heroin addict on suspicion of shoplifting.
He told another, a 21-year-old heroin addict: “You see what you do to us,” and groped her while sat in a patrol car in Newcastle.
He was sentenced in January, 2011, to life for rape, and ordered to serve a minimum of seven and a half years, minus 355 days on remand, before he was considered for parole.
He was also sentenced to a total of 29 years and three months on three charges of indecent assault, and six of misconduct in public office, to run concurrently with the life sentence.
Bodybuilder Mitchell – nicknamed PC Cucumber because of his cold, calculating demeanour during police interviews – has been told he can move into a hostel within days.
His victims have been informed of his imminent release.
One said: “I have lost all faith in the British justice system. This man should never have been a police officer, that was the only reason I ever met him.” A second victim added: “I thought he was going to jail for life.”
Mitchell was convicted after a five-week trial at Newcastle crown court in 2010. His victims wept as they heard Mitchell had “ruthlessly exploited” them and “degraded them repeatedly”
In 2014, it emerged the cost of the case was around £300,000 – more than £200,000 in compensation to his victims, and another £100,000 paid to their solicitors.