By Matthew Chapman
BBC Five Live Report
Pc Jonathon Bell took a month off for stress
The RSPCA has been accused of harassing a police officer after he killed an injured cat with a spade.
A prosecution estimated to have cost a total of £50,000 lasted two years before failing in the High Court.
The Police Federation says Pc Jonathon Bell had been "to hell and back" but the RSPCA says the case was in the public interest.
The charity pursues around 1,000 cases a year and that is likely to increase under the new Animal Welfare Bill. In April 2004, Pc Bell was called out to an estate in Stoke-on-Trent following reports of youths throwing stones at passing cars.
While there local residents called his attention to a cat which had been run over.
The 36-year-old officer sought advice from his control room and colleagues including a police handler.
He was told that by law there was no statutory duty for the police to call out a vet and that the RSPCA could not be contacted at that time of night.
He borrowed a spade and with three to four blows killed the cat.
His actions on that night unleashed what his supporters say has been a legal and personal nightmare for the officer who eventually was forced to take a month off because of stress.
The RSPCA says it took legal action following complaints from witnesses to the killing.
The officer was acquitted at a two-day court hearing last September.
District Judge Graham Richards said Pc Bell had been forced to make a decision in difficult circumstances.
"You did what you honestly thought best," said Judge Richards, "You walk out of here without a stain on your character."
But the animal charity made an appeal to the High Court which recently threw out the case. The final judgement came two years after the cat was killed.
"He thought he was doing his duty as a policeman in a difficult situation and he had to make a judgement call and he's been made to pay for it," Mark Judson, chairman of the Staffordshire Police Federation told Radio 5 Live.
He said Pc Bell was too traumatised by the long-running case to comment but that he felt "harassed" by the RSPCA, especially after the charity took the case to the High Court.
"They wouldn't let it go even when the decision had gone against them."
An independent expert witness called to give evidence in the trial said the officer had been in a no-win situation.
"The cat had been squashed to within an inch thick at its lower half," said veterinary surgeon Colin Vogel.
"He did the kindest thing which was to put it out of its misery whereas if he'd just walked away leaving it injured he could have just as easily faced a charge of animal cruelty."
The estimated £50,000 total cost of the case, which includes £12,000 spent by the RSPCA on its own legal costs, will lead to accusations that it has wasted large amounts of voluntary donations and public money.
The RSPCA has defended its role in the trial of Pc Bell as well as the 1,000 prosecutions it brings every year.
"In the end, the High Court refused the society's application for a judicial review. However, the RSPCA is pleased that Staffordshire Constabulary have since reviewed their procedures with regard to injured animals."
Matthew Chapman's report, The Policeman and the Dead Cat can be heard on Five Live Report on Sunday 9 April at 1100 BST and 1930BST and will also be available at the Five Live Report website.