The Taser stun guns used by officers attempting to stop gunman Raoul Moat from killing himself did not have Home Office approval, it has emerged.
An inquest into the 37-year-old's death heard two officers from West Yorkshire police fired the stun guns at him.
The XREP Tasers used are still undergoing tests however the government has said forces have discretion to use any equipment they deem necessary.
Moat died after a six-hour stand-off in Rothbury, Northumberland, on Saturday.
Details of the use of the Tasers were revealed during the opening of the inquest into Moat's death. The inquest was later adjourned.
A spokesperson for West Yorkshire Police said the officers involved have not been suspended from firearms duties and have returned to work.
Newcastle coroner David Mitford said Moat died as a result of a gunshot wound to the head.
Code of practice
The Independent Police Complaints Commission (IPCC) said in a statement that officers had used a long range XREP Taser - which has a range of about 100ft (30m) and operates without wires.
A Home Office spokesman said the XREP Tasers were "currently subject to testing by the HOSDB (Home Office Scientific Development Branch)".
He added: "However, legally, police forces have discretion to use any equipment they see fit as long as the use of force is lawful, reasonable and proportionate.
"The process for approval of less lethal weapons is set out in a Home Office code of practice document on police use of firearms which chief constables must 'have regard to'."
It is not clear whether the Tasers were fired before or after Moat apparently shot himself, Independent Police Complaints Commission investigator Steve Reynolds told the hearing at Newcastle Civic Centre.
He said: "At 1.12am Mr Moat's shotgun discharged, resulting in him receiving fatal injuries.
"At some point around the time of the fatal shot two West Yorkshire firearms officers armed with Tasers discharged their weapons at Mr Moat.
"This was understood to have been in an effort to prevent Mr Moat taking his own life."
The hunt for Moat began on 3 July after he was suspected of shooting his ex-girlfriend Samantha Stobbart, and murdering her partner, Chris Brown, in Birtley, near Gateshead.
Pc David Rathband was shot the following day in East Denton as he sat in his patrol car.
After a week on the run Moat was discovered armed on the riverbank at about 1900 BST on Friday and negotiators were brought in to speak to him.
Moat was pronounced dead in hospital at 0220 BST.
In a separate development, three further men were arrested on Tyneside earlier on suspicion of assisting an offender.
Two were arrested in Gateshead and one in Newcastle, bringing the total number arrested in connection with the inquiry to 10.
Four men and a woman arrested on suspicion of assisting an offender have been bailed.
Two other men have been charged with conspiracy to commit murder and possessing a firearm with intent.
Meanwhile Metropolitan Police Commissioner Sir Paul Stephenson has criticised tributes which have been paid to Moat.
Flowers and cards have been left at the scene of Moat's death and outside his home in Fenham, Newcastle, while almost 17,000 people have joined a Facebook group called RIP Raoul Moat You Legend.
One of the cards in Fenham read: "A good mate, a good dad, good at school, well-mannered, hard-working businessman. That's the real Raoul Moat."
Sir Paul said the tributes were "extraordinarily disappointing".