A fresh inquest has been ordered into the death of man who died while waiting for an ambulance.
Carl Bibby, 38, was found to have suffered a cardiac arrest in his flat in Kirkby, Merseyside, in July 2009.
The High Court ruled that a previous inquest jury should have been allowed to decide whether an ambulance delay was a factor in the death.
The decision follows a legal challenge by Mr Bibby's family.
The High Court judges, Lord Justice Gary Hickinbottom and Justice Ed Pepperall, found that "the coroner erred in law and that the issue of the causative effect of North West Ambulance Service's (NWAS) admitted delay should have been left to the jury".
The court was told that a neighbour heard banging and screaming inside Mr Bibby's home on July 27, 2009 and called the police.
NWAS were called at 23:54 and again at 00:10, 00:36 and 00:38 but the first ambulance did not arrive until 00:46, by which time Mr Bibby was not breathing and paramedics could detect no electrical activity from his heart.
Police officers restrained Mr Bibby while waiting for the ambulance, the judges found, during which time "his body went limp".
Emergency services staff gave evidence that "the failure to upgrade the case in response to the call at 00:10 had been an error", the judges found.
Despite this, the previous coroner ruled that the cause of Mr Bibby's death was "unascertained" and said he was not satisfied that the conduct of the police and ambulance personnel amounted to "a gross failure for the purposes of neglect."
The High Court decision came after Mr Bibby's brother, John Chidlow, challenged the original inquest verdict.
A spokesman for Broudie Jackson Canter, the law firm representing the Bibby family, welcomed the decision to quash the original findings.
"The High Court have ruled that the issue of the causative effect of North West Ambulance Service's delay in attending to Carl should have been left to the jury," he said.