A sergeant who told a junior officer to destroy a dead colleague’s mobile phone to stop his family finding out about a secret affair must leave his force, the Appeal Court has ruled.

Sgt Neil Salter instructed PC Scott Mesher to find and destroy the phone belonging to DC Ian Morton, who had died in a road traffic collision, as it contained text messages which “evidenced” DC Morton’s relationship with a female officer from another force.

The Dorset Police sergeant, who had an “unblemished career” as an officer for 22 years, had been in touch with the female officer before his discussion with PC Mesher – but the decision had been “his alone”, the court noted.

DC Morton died in October 2008 and had a long-term partner who was unaware of the affair. However, the coroner already knew of the “illicit relationship” by the time Sgt Salter decided to act.

The court heard that PC Mesher refused to go to carry out the request and instead told senior colleagues.

Sgt Salter admitted full responsibility and said PC Mesher had been right to speak out against him.

Lord Justice Maurice Kay said: “There was a statement from PC Mesher saying that he believed Mr Salter’s decision had been the result of misguided loyalties towards the family of DC Morton and made to protect them from further upset. Other officers gave statements to the same effect.”

Sgt Salter was found guilty of “a very serious breach of integrity” by a misconduct panel in August 2009 and ordered to resign. This was verified by a chief constable’s review in November the same year.

But the Police Appeals Tribunal (PAT) later ruled Sgt Salter should be reinstated at the rank of constable as dismissal “is reserved for the most serious cases”. The chief constable applied for judicial review and the High Court quashed the PAT’s decision in late 2011.

At Sgt Salter’s appeal, three judges ruled the Judicial Review decision was correct – and that the PAT had exceeded “the limits that were reasonably open to it”.

Lord Justice Gross said: “This is a very sad case indeed and I find it impossible not to have sympathy for Mr Salter.

“His insuperable difficulty, however, it that the operational integrity of the police is of fundamental importance.

“A central role of the police involves the gathering and presentation of evidence.

“The destruction of evidence is inimical to the office of constable all the more so, when it entailed an instruction to a junior officer to do so.

“For my part too, the practical problems that would attach to any future deployment to Mr Salter as a police officer reinforce the conclusion to which I feel driven to come.”

Sgt Salter had been appointed the Deputy SIO following DC Morton’s death and PC Mesher the Family Liaison Officer.