A man who died after being restrained by five police officers for almost an hour, mostly face down on the ground, after a 999 call reported that he was “acting strangely”, is one of more than 40 in Britain whose deaths were subsequently blamed on a disputed medical condition. Bodyworn camera footage captured Krystian Kilkowski, 32, an engineer from Poland, saying he feared he would die as police held him down outside his house in Diss, Norfolk, in August 2020. By the time an ambulance arrived he was breathing and covered in blood, having bitten his arms and tongue in distress. A 2022 inquest later heard he had taken amphetamines, but not a fatal dose, and that “serious failures’ in the use of restraint by Norfolk Police contributed to his death. The Independent Office for Police Conduct recommended further training but cleared the officers of any blame, saying in its report that Kilkowski had been suffering from “acute behavioural disturbance” (ABD). His death was recorded as “drug related” on his death certificate, with ABD – exacerbated by “physical activity” and the police restraint – listed as a contributing factor. But the label is fiercely contested within medicine, rooted in pseudoscience and is not a diagnosis recognised by the World Health Organization. The original evidence upon which the “condition” was based – which claimed that 32 black women found dead in Miami in the 1980s had dropped dead suddenly after going into states of “excited delirium” due to sex and cocaine - has been debunked as pseudoscience after they were in fact found to have been murdered. Even so, reference to the condition, now known more commonly in Britain as “acute behavioural disturbance” – has controversially persisted. It is now most commonly used to describe people who are agitated or acting bizarrely, usually due to mental illness, drug use, or both. Guidance from the Royal College of Emergency Medicine says ABD is an umbrella term used to describe a presentation characterised by symptoms such as insensitivity to pain, increased strength and elevated heart rate. Over recent years, the labels have come under increased scrutiny. In the US, “excited delirium” (ED) emerged as an issue during the trial of police officers implicated in the murder of George Floyd, following controversial suggestions he had been suffering from it at the time of his death. In January, a podcast by journalist Jon Ronson, Things Fell Apart, detailed how police and lobbyists in the US have used “excited delirium” as an explanation in court following the deaths of hundreds of people tasered over the years. The American Medical Association and other influential health organisations have rejected the terms as a cause of death or diagnosis following concerns they were being used to “explain away” police involvement. Campaigners fear a similar pattern in Britain, where ABD is routinely cited as a factor in sudden and mysterious deaths following police contact – predominantly of black men and those from ethnic minorities. “Acute behavioural disturbance” and “excited delirium” have been referenced as a cause of death, or a contributing factor, in police watchdog reports and inquests in least 44 restraint cases since 2005, according to research by the charity Inquest, the Royal College of Psychiatrists and the Observer, including as recently as last month. Deborah Coles, executive director at Inquest, said it had “without a doubt” been used in some cases to downplay the “inherently dangerous” use of restraint. Hers is a fear shared by Stephen Ball, whose son Joshua Ball, 26, died after being restrained in 2018. Before hand-cuffing him and placing a spithood over his head, Staffordshire police discussed whether he had ABD or ED and noted he was presenting in an agitated state, displaying incoherent speech and a high body temperature. At the time, Ball had taken cocaine, was acting bizarrely and was bleeding with an injury to his stomach after a member of the public threw a rock at him. The police log for the incident referred to “excited delirium”, adding: “He is very excitable do not believe to be life threatening.” Ball, a father of one described by his family as a “cheeky chap”, later suffered two cardiac arrests. An inquest concluded the rock injury and cocaine use were likely to blame, but highlighted concerns over “inappropriate police restraint and use of a spithood”. The police watchdog report, which referred to ABD, referred one officer for further training but found there was no disciplinary case to answer, concluding the use of force was “necessary, reasonable and proportionate”. Stephen Ball, said he feared ABD and ED offered police a “blinding excuse to overreach” on their use of force, under the guise of preventing harm. “It gives the restrainers an excuse of: ‘Well what else could we do?’,” he said. “My first and only glimpses of Joshua on video told me he required medical attention not further violence or physical restraint.” Staffordshire Police called Ball’s death “untimely and tragic”. In relation to references to “excited delirium” in police logs, it said: “We haven’t used the term ‘excited delirium’ for some time. The phrase ‘emotionally or mentally distressed’, which is referred to in College of Policing guidance, is now used, which describes individuals who may behave in an unexpected, extreme or challenging manner as a result of a mental health issue or emotional distress, or which may, on occasion, be caused by self-medication.” Acute behavioural disturbance was also referred to in the case of Mouayed Bashir, a 29-year-old man of Sudanese heritage who died after being restrained in the bedroom of his family home in Newport, South Wales, in 2021. Speaking to the Observer after the inquest into Mouayed’s death last month, his family described him as a “lovable” and smiley hip-hop lover who cared for his poorly mother and dreamed of opening his own restaurant. In the days before he died he had suffered deteriorating mental health, which spiralled on the morning of 17 February, 2021 after he had taken cocaine. His parents called a GP, and then 999, for help. Police arrived before the paramedics. Officers later said they feared that Mouayed, who had past convictions related to possession of cannabis and pepper spray, was armed. But when they entered his room they found him lying on the floor in his underwear, kicking out, and said he appeared to be suffering a “mental episode”. They handcuffed him, strapped his ankles and knees, and restrained him as he twitched, moaned and cried out. Mouayed’s health, including his oxygen levels, deteriorated, and he fell unconscious. He later went into cardiac arrest. The inquest concluded that he had taken “an unknown quantity of cocaine which resulted in him developing symptoms in keeping with ABD”. The use of force was found by the IOPC to have been reasonable. Before restraining Mouayed, and in subsequent incident forms, officers said they believed he had ABD. Mouayed’s brother, Mohannad Bashir, 35, said there had been “no accountability” following Mouayed’s death, and that he needed medical help, rather than restraint. He said he was concerned ABD could be used as a “shield” or a “cover for fault”, and called for its use to be reviewed. “It’s a pattern. A lot of young black men who die under police restraint fall under the ABD category,” he said. “They treated him as a criminal not as a person who was desperately in need.”