PC Benjamin Monk, of West Mercia Police, was convicted of the killing after jurors reached a unanimous verdict at Birmingham Crown Court today.
The 42-year-old Tasered the ex-Aston Villa striker for 33 seconds before kicking him twice in the head “like a football”.
The 48-year-old retired footballer was rushed to hospital following the attack outside his father’s home in Telford, Shropshire, but died after suffering a cardiac arrest.
Following the jury’s verdict, Atkinson’s family said in a statement: “On the night he died, Dalian was vulnerable and unwell and needed medical attention. He instead received violence, and died with PC Monk’s boot lace prints bruised onto his forehead.”
No police officer in England or Wales has been found guilty of murder or manslaughter over a death in custody, or following police contact, since the 1980s, charity Inquest has said.
The 12-person jury took 18 hours and 48 minutes to unanimously clear Monk of murder, but found him guilty of manslaughter, also by a unanimous verdict.
Jurors are still deliberating on an assault charge relating to Monk’s colleague and former girlfriend, PC Mary Ellen Bettley-Smith.
The court heard that Monk and his partner at the time, Ms Bettley-Smith, 31, were called at 1.30am on August 15 2016 after Atkinson tried to smash his way into his father’s house.
Monk told the court he ran in fear as Atkinson appeared to be having a mental health crisis, and 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.
However, prosecutors said that Monk used unlawful and unreasonable force out of anger, through a 33-second firing of his Taser and by kicking Atkinson in the head.
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.
Witnesses described how Monk continued to batter Atkinson even after he appeared to be “dead” on the floor.
The former Villa, Sheffield Wednesday and Ipswich Town striker was rushed to Princess Royal Hospital in Telford, but died at 2.54am.
Following Atkinson’s death, Monk was accused of lying about kicking him in the shoulder to cover his tracks.
Neighbours told the court how they witnessed Monk lashing out in a “really violent stomping action” and kicking Atkinson “like a football”.
Jean Jeffrey-Shaw said: “I was traumatised from what I saw, it was a nightmare. He was stamping his foot down.
“He was kicking his head and stamping on it and I had to look away as I couldn’t keep up; it was too much for me and I had to look away.”
Jurors were told how the use of the Taser and the kicks contributed to Atkinson‘s death, despite his underlying health conditions.
In footage of his police interview released after the case, Monk can be heard saying: “I formed the opinion that the only way to keep this man on the ground to ensure our safety was to kick him. And that’s what I did.”
Additional reporting by agencies