Jurors at Birmingham Crown Court took 18 hours and 48 minutes to reach unanimous verdicts on Pc Benjamin Monk, who claimed he was put in fear of his life by the former Aston Villa, Sheffield Wednesday and Ipswich star on August 15 2016.
Jurors are still deliberating on an assault charge relating to Monk’s colleague and former girlfriend, Pc Mary Ellen Bettley-Smith.
According to the charity Inquest, no police officer has been found guilty of murder or manslaughter over a death in custody or following police contact in England and Wales since the 1980s.
The last time an officer was convicted in such a case was in 1986, when a Merseyside police sergeant was found guilty of manslaughter after kicking and punching a retired bus driver in a police cell.
Monk told the court he ran in fear after Atkinson, who appeared to be having a mental health crisis, made death threats and smashed a glass door pane at his childhood home in Meadow Close, Telford, Shropshire.
The 43-year-old officer claimed the former Premier League star was trying to get up when he aimed kicks at his shoulder in lawful self-defence as a last resort, after running out of Taser cartridges.
Mr Atkinson went into cardiac arrest after being taken from the scene in an ambulance, and was pronounced dead in hospital at 2.45am – about an hour after he was Tasered.
Prosecutors said Monk lied about the number of kicks he had delivered to the victim’s head by claiming he could remember only one aimed at his shoulder.
The officer also claimed to have no recollection of placing his foot on Atkinson’s head as colleagues arrived at the scene.
Although he conceded he must have kicked the ex-footballer twice in the forehead because bootlace prints proved he had, the officer maintained his actions were lawful self-defence made necessary when Atkinson tried to get up.
Taser records showed Monk activated the weapon eight times for a total of more than 80 seconds using three Taser cartridges, culminating in a 33-second deployment more than six times longer than is standard.
Jurors were told they could convict Monk of murder only if they were sure he intended to cause really serious injury.
The jury was instructed to find Monk guilty of an alternative charge of manslaughter if they were not sure he intended to cause serious harm but the force used was an act any reasonable person would realise was bound to pose a risk of physical harm.
The court heard that Monk, who has 14 years’ service in uniform, and Bettley-Smith, who joined the force in February 2015, were in a relationship at the time of the incident.