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".
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.
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.
Footage of the moment a police officer fired a 50,000 volt stun gun at a naked suspect in a custody cell has been leaked to ITV News. Today a jury at Bristol Crown Court cleared the officer of assault, and the Chief Constable of Wiltshire tried to stop any of the film from being shown.
A 26-year-old man has been arrested after up to 30 cars were damaged with a hammer in Bristol.
Officers and a police dog unit were sent to Rodbourne Road in Horfield this morning after complaints from the public. The man was arrested after a Taser and baton round were deployed.
Avon & Somerset Police have referred the incident to the Independent Police Complaints Commission
A convicted murderer who had been on the run since last Saturday has been recaptured by police in Bristol. Paul Flint, 47, was finally caught after being tasered by officers outside a house in Bedminster where his brother lives.
Flint had disappeared from an open prison in Suffolk. He was jailed in 1990 for murdering the occupant of a house he had burgled in London.