Avon and Somerset Police is under investigation into what led officers to use a Taser on a vulnerable man with autism and learning difficulties.
The 26-year-old was Tasered in August last year before he was arrested and charged with assaulting a police officer and criminal damage.
But the charges after the incident in Bristol were later dropped by the CPS, and now the police watchdog is investigating whether the use of the Taster was "proportionate".
Our investigations, which are at early stages, will look at how police discharged their duties and responsibilities while dealing with a man deemed to be vulnerable, and whether appropriate force was used.
It is important that we establish the full facts, and we will regularly update the complainants and police force as our enquiries progress
The investigation follows a complaint from the man's mother who alleges police failed to properly investigate, or provide appropriate support, for him despite his health problems.
The Independent Police Complaints Commission (IPCC) is also investigating how the force dealt with the same man on three separate occasions in 2014.
Two incidents saw the man convicted of burglary and harassment, while the CPS decided not to proceed with one charge of assault.
We can confirm that we voluntarily referred this incident to the IPCC who are carrying out an independent investigation.
We are not able to comment further at this stage.
The Independent Police Complaints Commission has recommended that training in the use of Tasers should be revised, following the death of a man from Plymouth.
Andrew Pimlott died from severe burns after dousing himself in petrol at his parents' home in April 2013.
An inquest decided yesterday that he had probably caught fire after being Tasered by police.
You can read the full IPCC report here.
A police taser was the 'most likely' cause of a man catching fire and dying, an inquest jury concluded today.Read the full story ›
An inquest is underway into the death of a man tasered by police officers after he doused himself in petrol while holding a lit match.
Andrew Pimlott died several days later as a result of the severe burns he suffered.
Our reporter Richard Lawrence sent this report from the hearing:
An inquest has heard how a police officer who tasered a man who'd doused himself in petrol had never used the weapon before.Read the full story ›
An inquest has heard how a police officer tried to prevent a man who was covered in petrol setting fire to himself in Plymouth - by shooting a Taser at him.
PC David Beer described the moment his colleague fired the stun gun which led to Andrew Pimlott's death in April 2013.
PC Beer told the court that he arrived at the garden of the house in Coombe Park Lane to join his colleague and saw Mr Pimlott dowse himself in petrol.
He then saw him strike something and saw the flame. He said he thought there was an immediate risk to everyone nearby. He heard PC Hodgkinson's Taser activate and saw Mr Pimlott covered in flames. He covered him in a duvet, then people rushed in with water and paramedics arrived.
Mr Pimlott died in hospital five days after the incident.
PC Peter Hodgkinson says the incident was the first time he had deployed the Tazer.
The Crown Prosecution Service previously decided that there was insufficient evidence to bring any charges against the officers involved.
The father of Andrew Pimlott told the inquest that he thought his son was "calling his bluff" when he grabbed the petrol can.Read the full story ›
An inquest has heard how a man was tasered by police officers after he doused himself in petrol while holding a naked flame died.Read the full story ›
A police officer who tasered a man who'd doused himself with petrol in Plymouth will not face criminal charges - but could face a gross misconduct hearing.
Andrew Pimlott, who suffered fatal burns when he was hit by the stun gun in April 2013, had poured petrol over himself and was holding a lit match at the time.
Tasers should only be used in the most exceptional circumstances. That's the finding of the Independent Police Complaints Commission, in a report on the use of the defence weapon by forces.
A policeman in Wiltshire, PC Lee Birch, was recently cleared of ABH and misconduct for Tasering a naked suspect.