The appeal of a former nurse convicted for the murders of four elderly patients is “a straightforward case”, the Court of Appeal has heard in the final days of his challenge.

Colin Campbell, formerly known as Colin Norris, was found guilty in 2008 of killing four women and attempting to kill a fifth by injecting them with insulin.

Doris Ludlam, Bridget Bourke, Irene Crookes, and Ethel Hall, were inpatients on orthopaedic wards where Campbell worked in Leeds in 2002 before they died and developed severe, unexplained hypoglycaemia.

Prosecutors relied on a “wholly circumstantial” case, the Criminal Cases Review Commission (CCRC) said after referring the case to the Court of Appeal in London four years ago.

On the 13th day of the appeal hearing in London, judges heard closing submissions from Campbell’s barristers.

In written submissions, Michael Mansfield KC said: “The appellant submits that this is a straightforward case in which this court must conclude that these convictions are unsafe.”

Campbell denied any wrongdoing and said he did nothing to cause hypoglycaemia in any of the patients.

Colin Campbell outside Newcastle Crown Court in 2008, where he appeared charged with murdering four patients at Leeds hospitals.

placeholder image — Colin Campbell outside Newcastle Crown Court in 2008, where he appeared charged with murdering four patients at Leeds hospitals.

He unsuccessfully appealed against his conviction in 2009 and applied to the CCRC in 2011.

The Crown Prosecution Service is opposing the appeal.

James Curtis KC, for the CPS, told the court that there were “certain matters to which we take exception” from the closing submissions provided on behalf of Campbell.

He said: “There are a number of matters that I would seek to issue corrections on, things we firmly disagree with my learned friend on.”

Mr Curtis is expected to make closing submissions on Friday.

The appeal before Lady Justice Macur, Sir Stephen Irwin and Mr Justice Picken is due to conclude on Friday.