A 50,000-volt police Taser was the "most likely" cause of a petrol-soaked man catching fire and dying, an inquest jury has ruled.
Andrew Pimlott, 32, poured the fuel over himself when Pc Peter Hodgkinson fired the weapon at him during a domestic incident in the back garden of his parents' house on the evening of April 18 2013.
Pc Hodgkinson and his colleague, Pc David Beer,had answered a 999 call from Mr Pimlott's father, Kelvin, reporting that his son was carrying a jerry can of petrol, may have a lighter and was breaching a restraining order imposed by magistrates to stay away.
Just 41 seconds after the two officers arrived on the scene in Honicknowle, Plymouth, Mr Pimlott erupted into a human fireball - dying five days later in hospital from severe burns.
The two officers insisted that Mr Pimlott was holding a lit match but, in a narrative conclusion, the jurors said they had decided "we don't know" whether he was holding a flame or not, although he was in possession of matches.
"We believe that the Taser was the most likely source of ignition," they said. "We believe that an exchange of words indicating 'Put it down' was said before the Taser was discharged. We don't know how soon after the Taser was discharged."
The jury said Pc Hodgkinson's actions were "in accordance" with his training.
The experienced officers told the inquest that when Mr Pimlott was standing, soaked in petrol and with a lit match in his hand, they had no other choice in trying to save his life but to shoot him with the Taser X26.
Pc Beer described his immediate reaction to seeing Mr Pimlott as: "F****** hell, he's going to go up."
And his colleague told the Plymouth inquest: "I thought he was about to use the flame that was in his hand to set himself alight and if I didn't take any action that he was going to harm himself and I needed to use the Taser to stop him harming himself."
Neighbours heard screams coming from the garden, saw flames and also watched as the two officers wrapped Mr Pimlott in a duvet and sprayed him with a hosepipe to extinguish the flames.
Afterwards, Mr Pimlott, who was a known binge-drinker, told both an ambulance technician and a nurse that it was the Taser that had caused him to catch fire.
A pathologist said there was no medical evidence to say how Mr Pimlott caught fire but a forensic scientist said it was his opinion, as an experienced fire investigator, that the Taser was the cause.
Following the incident, a single match was recovered from the garden and a box of matches was found in Mr Pimlott's trouser pocket.
Kelvin Pimlott told the inquest: "I never thought Andrew would set fire to himself. I thought he may have been trying to frighten us and call our bluff."
Earlier this year, Pc Hodgkinson was cleared of gross misconduct following an internal disciplinary hearing.
The Crown Prosecution Service had already decided there was not enough evidence to charge him because he was trying to save Mr Pimlott's life.
Pc Hodgkinson had completed a three-day nationally-approved Taser course in November 2012 and the night he faced Mr Pimlott was the first time he had used the weapon since completing his training.
Witnesses told the hearing that national training guidelines warn of the potential dangers of firing a Taser in the presence of flammable liquids due to the risk of ignition but do not prohibit it.
And Pc Hodgkinson's decision-making process was "consistent" with the rules governing the use of the weapon, Taser training expert Gary Wedge told the hearing.
Sergeant Wedge ruled out using an extendable baton, the Pava irritant spray or trying to use direct physical force on Mr Pimlott because it would mean getting too close and risk ignition.
"It is impossible to predict Andrew's actions after lighting the match but it would be reasonable for the officers to conclude that it was his intention to set fire to himself and presented a risk to the officers," he said.
"Putting it bluntly, there were no easy answers to these set of circumstances."
The case of Mr Pimlott is one of a number of controversies involving the use of stun guns by police.
Since the introduction of Tasers in 2003, Home Office figures show their use has increased by more than 200%, with one in 10 officers now armed with a Taser and more than 10,000 Taser incidents in England and Wales in 2013.
In June, an inquest jury concluded that Jordon Begley, 23, died as a result of being Tasered and restrained by Greater Manchester Police officers two years ago.
Blind pensioner Colin Farmer was hit with one of the weapons in Chorley, Lancashire, when an officer mistook his white stick for a Samurai sword.
In 2012, James McCarthy suffered a heart attack after he was hit twice with a Taser at a hotel in Liverpool.
And in December 2013, a teenage boy with complex learning difficulties was Tasered in the grounds of a special school owned by the exclusive Priory Group - Chelfham Senior School, near Plymouth.
Since 2004, there have also been two cases where epileptics have been Tasered - one of whom was already having a seizure, and one of whom began having one after being struck.
After the jury returned its conclusion, Plymouth Coroner Ian Arrow heard that the IPCC wrote to the National Police Chiefs' Council (NPCC) recommending that officers are given "more comprehensive guidance" about the user of Tasers in the presence of flammable liquids.
"It is clear from this incident that Taser should only ever be considered for the use in the presence of flammable substances as a last resort and after every other available option has been considered and discounted," IPCC commissioner Tom Milsom said in his letter to Commander Neil Basu, police lead for Taser at the NPCC.
"Furthermore the IPCC will be referring this case to the College of Policing to feed into the current review of Taser training which is taking place."
The inquest heard that in his reply to the IPCC, Mr Basu said: "From the contents of this letter steps have already been taken to further enhance the training given to officers in relation to the use of Taser.
"However we do not consider it appropriate to use the wording you suggest in respect of 'Taser should only ever be considered for use in the presence of flammable substances as a last resort after every other available option has been considered and discounted'.
"However we do appreciate and understand that the use of Taser when a subject has doused themselves in petrol is exceptional.
"The discharging of a Taser against a subject who has doused themselves in petrol is highly likely to result in the ignition of the petrol potentially resulting in serious and fatal injuries and therefore Article 2 of the European Convention on Human Rights is likely to be engaged.
"Any decision to use Taser should therefore be proportionate, lawful and absolutely necessary in the circumstances."
Ali Cloak, the solicitor representing the Pimlott family, read a statement on their behalf.
She said: "Andrew's family have considerable concerns in respect of the use of the Taser which caused the fire and the burns from which Andrew died.
"In particular the family are concerned that a Taser was used in circumstances where the training in respect of Tasers makes it clear that, in dealing with any substance you can ignite with a match, you should expect a Taser to have the same effect, and also that the officers did not attempt to resolve the issue by communicating with Andrew instead.
"Whilst Andrew was in some ways a troubled young man, he was a loving son, brother and uncle and he will be very much missed by his family."
Chief Superintendent Jim Nye, of Devon and Cornwall Police, said: "Devon and Cornwall Police note the findings of the jury and the comments of the coroner in relation to the prevention of future deaths.
"Our condolences remain with the Pimlott family regarding the death of Andrew.
"As the coroner noted, the death of Andrew has had an impact not only on the family but also the officers involved.
"Any officer using Taser is subject to extensive training, and we should not under-estimate the challenging circumstances police officers face in their line of duty.
"Difficult decisions sometimes need to be made in highly pressured situations.
"Devon and Cornwall Police has always followed national guidance and training regarding the use of Taser.
"We will follow with close interest any developments resulting from the IPCC's recommendations to the National Police Chiefs' Council and the College of Policing."