A written apology by police has been sent to the family of ex-footballer Dalian Atkinson, six months after an officer was jailed for manslaughter.
The officer had Tasered him and kicked him in the head, as West Mercia's chief constable Pippa Mills said she was "deeply sorry".
"A police uniform does not grant officers immunity to behave unlawfully or to abuse their powers," she wrote.
PC Benjamin Monk's conviction was the first for a death in custody in 30 years.
In the wake of the Black Lives Matter movement, the family of Atkinson, a former Premier League star footballer with Aston Villa, said the case has showed how black people are treated by police and the criminal justice system.
Mills took over as chief constable of West Mercia Police in September, three months after the legal proceedings ended.
In her letter to the family she wrote that due to European Convention on Human Rights, there was an "obligation" for her to "acknowledge and accept" on the behalf of the force that Atkinson's human rights were breached.
"Ben Monk's conduct was in direct contradiction to the standards and behaviour of the policing service, and understandably undermined public confidence," she said.
She added: "I am deeply sorry for the devastating impact the actions of a West Mercia officer has caused you and I extend my deepest condolences to you all, and Dalian's wider family and friends."
Mills added that the incident was "devastating" for the family, saying: "I cannot imagine the immense pain you have felt and how the significant delays with the trial have also added to your burden of grief.
"You have demonstrated great strength and dignity throughout the past five years."
Atkinson, who was suffering from a serious illness that had affected him mentally and physically, died in hospital in 2016 after he was arrested outside his father's home in Telford, Shropshire.
Police officers work in Meadow Way, Trench, Telford at the scene where former Aston Villa player Dalian Atkinson was tasered by police on August 15, 2016. (Photo by Christopher Furlong/Getty Images)
The former footballer was in the midst of a mental breakdown when he was shouting outside his father's home, that is when the neighbours reported.
Monk reportedly used his taser on the 48-year-old for 33 seconds and kicked him to leave footprints of his boots on Atkinson's forehead. The judge at Monk's trial destribed his actions as an "obvious" use of excessive force. Monk was jailed in June for eight years, for the first time in three decades a British police officer was convicted of manslaughter.
A lawyer for Atkinson's family, Kate Maynard, said in a statement the official apology is "welcomed and overdue".
"The chief constable's acknowledgement that a police uniform does not grant immunity is especially pertinent in a year that has seen other terrible examples of deadly police violence," she said.
"With the first conviction of a serving police officer on a manslaughter charge connected with his policing duties in over 30 years, it is hoped that this will serve as a deterrent, and also embolden those who seek police accountability."
