Zahir Aziz was assessed as 'low risk' when he came out of prison for GBH. But he went on to murder his uncle, Shabir Choudary, from Wakefield, in January 2010 - just a month after his release.
West Yorkshire Probation Service have now admitted he should have been assessed as 'high risk', which would have led to him being recalled to prison when he breached his terms.
Mark Siddall, Director of Operations for West Yorkshire Probation Trust, said: “On behalf of West Yorkshire Probation Trust I would like to express our sympathy with the family of Shabir Choudary for their loss.
"It is extremely rare for an offender under our supervision to commit a serious crime, but every case is one too many.
“A thorough investigation of this case was carried out and it found that, while the overall case management was good, the initial risk assessment carried out fell short of the appropriate professional standard."
"Our internal review made recommendations to improve practice and these were implemented. We continually improve our practice as the result of learning from all Serious Further Offence Reviews, including those from other Probation Trusts, and analysis of our day-to-day work.
“Members of the victim’s close family were contacted by West Yorkshire Probation’s Victim Services Unit directly after the offence to offer immediate and ongoing contact about the case. They were also invited to meet with the Head of Wakefield Probation to discuss the case and the next steps for West Yorkshire Probation, including the Serious Further Offence Review. This meeting occurred on 2 September 2010."
Nesar Rafiq, Choudary's nephew, is also campaigning for Serious Offence Reviews to be available for the family if they want to see them. He is being supported in this by Wakefield MP Mary Creagh.
However, Mr Siddall added: “It is not normal practice to publish Serious Further Offence Reviews and these will not routinely be disclosed. The reports contain operational detail about the way in which serious offenders are managed and to routinely publish these details may jeopardise the way in which we carry out procedures to protect the public.
"They also contain information about other named individuals, which it would not be appropriate to publish. They are written to help Probation learn from the way a case was managed and to apply lessons for future cases.
“Unfortunately risk can never be completely eliminated but as the result of our thorough review we are determined to have the best possible systems in place to supervise offenders in the community and protect the public.”