The Independent Police Complaints Commission says Cumbria Police failed to finish lines of inquiry before releasing a man who went on to kill the partner he was accused of raping.
Miklos Verebes was jailed for life, for a minimum of 28 years, earlier this year after he was convicted of murdering Melinda Korosi in Carlisle in 2016.
In its report, the IPCC says Miklos Verebes was arrested on suspicion of rape and then released without charge.
Cumbria Constabulary released the following statement:
We acknowledge the findings of the IPCC’s investigation into the contact between the Constabulary and Melinda Korosi prior to her death.