Zara Aleena's aunt has called Labour's proposals to free thousands of criminals early a "dangerous gamble with public safety."
In the event that the probation service was unable to handle the situation, Farah Naz, whose niece was killed by a guy who had been released from jail on a nine-day license, issued a warning.
She said that in the case of Ms Aleena’s killer Jordan McSweeney, the probation service was "not fit to deliver supervision" or "act in a timely way" when he broke his licence conditions.
She told BBC Breakfast: “If the system cannot deal with those people being released into the community, then those people are not going to be supervised adequately.
"And when people, perpetrators, even thieves are not supervised adequately, crime can escalate. It doesn’t always escalate, but it can.
"Then we’ve got unsupervised people because of a poor probation service in the community and people become emboldened - ‘well I can do what I like if nobody is supervising me’ - and that’s what happened in our situation.
"It was a man that was emboldened because he was not supervised, he was not assessed, he was constantly allowed to do what he wanted to do, and therein lies a dangerous gamble with public safety with this move right now."
Law graduate Ms Aleena was killed by McSweeney as she walked home from a night out in June 2022.
Her aunt’s intervention comes as the new justice secretary, Shabana Mahmood, prepares to announce a string of measures to ease the overcrowding crisis in Britain’s prisons.
Among the expected measures are the automatic release of prisoners on standard determinate sentences after they have served just 40 per cent of their time. The current threshold is 50 per cent - but exemptions for serious violent and sexual offenders are expected.
There are fewer than 700 places remaining for adult men in UK prisons, which would be filled within weeks without action - with particular fears around the August bank holiday.
The usual buffer for prison places is more than double the current level, and if spaces fall below 300, they will have to stop accepting prisoners sent from courts.
"We’re operationally in trouble at less than 300 spaces left,” a senior prison source said.
Meanwhile police officials have warned that if prisons filled up, it would take just days for police cells around the UK to reach capacity as well. This would lead to a situation in which police were unable to arrest criminals, with sources fearful it could lead to unchecked criminality, with civil order potentially breaking down and widespread looting.
Ms Mahmood is expected to announce the emergency measures from a prison in Wellingborough on Friday afternoon, with officials having warned the crisis could not wait any longer.
The chairman of the Prison Officers Association has said the measures would give prisons around 12 to 18 months before further measures were needed, freeing up 4,000 to 5,000 spaces.
Asked if a potential move by the government to release certain inmates after serving 40% of their sentences was dangerous, Mark Fairhurst told BBC Breakfast: "We would hope it wouldn’t be, but what is more dangerous to the public is if we don’t act, so if we’re clogging up police cells they’re unable to arrest people because there’s nowhere for them to go.
"That’s more (of a) danger to the public.
"What we’re doing is releasing people early who are going to get released anyway at some point."
Prime minister Sir Keir Starmer said the Conservatives had left Labour to inherit a “broken” prison system and described his shock at the scale of the crisis.
Speaking to Channel 4 while attending the Nato summit in Washington, DC, Sir Keir said: “I’m shocked to be in this position, particularly having worked in criminal justice. It is a basic function of government that there should be enough prison places for the number of people that courts are sending to prison. That basic premise broke down under the last government, that is beyond irresponsible, and we’re going to have to pick up that mess and they ignored it.
“I can’t build a prison in seven days with the best will in the world. It is clearly a problem left by the last government. We cannot be in this terrible state and they ignored the problem, didn’t fix the problem, we are going to have to fix it.
“We have to make short-term measures that we will announce in due course and then of course we’ll have to do even further measures. I simply can’t build a prison in seven days.
“This is a terrible failure of the last government.”