Home Secretary Theresa May's hopes of deporting an Italian father-of-five who hit his flat-mate over the head with a hammer then strangled him with the flex of an iron have been dashed by senior judges.
The Court of Appeal concluded that the 54-year-old man should not be deported because he did not pose a "sufficiently serious threat to public security".
Mrs May had challenged a similar earlier ruling by an Asylum and Immigration Tribunal.
Lord Justice Pill, Lord Justice Aikens and Lady Justice Rafferty dismissed her appeal after a hearing in London. The man was not identified in the appeal judges' written ruling - and the ruling did not explain why he was not identified.
Appeal judges said the man had been given an eight-year jail term in 2002 after being convicted of killing flat-mate Edward Mitchell.
Judges said the man had been convicted of manslaughter by a jury at the Old Bailey. They said he had struck Mr Mitchell "at least 20 blows to the head with weapons, including a hammer" before strangling him.
They added that jurors decided that "murder was reduced to manslaughter by reason of provocation". They said the man had been released from prison to "hostel accommodation" in 2006 but, because no place was available, he had been re-arrested.
The man had subsequently received damages of £25,000 for the "unlawful imprisonment which followed", judges said.
He also had convictions for "assault on police", battery and "having a bladed article", the appeal court heard.
A UK Border Agency spokesman said: "We are very disappointed that the court has ruled we cannot deport this individual. We have appealed against that decision and hope that we will be able to pursue his removal from the UK."