The family of a mentally ill man who died in police custody said he was restrained “unnecessarily and disproportionately”, as a jury found it contributed to his death.
An inquest at Southwark Coroner's Court heard that the 35-year-old told officers “I'm going to die” and “I can't breathe” as he was put into handcuffs due to his size.
He lost consciousness as he was taken to an ambulance.
Returning a narrative conclusion on Friday after five days of deliberations, an inquest jury found that the decision to use restraints on Mr Clarke was “inappropriate”.
The jury concluded that it was also “highly likely” that at least one officer heard Mr Clarke say “I can't breathe” on more than one occasion.
Speaking after the inquest, his sister Tellecia Strachen said: “Those involved in his death saw him as the stereotype big, black, violent, mentally unwell man.
“KC was restrained unnecessarily and disproportionately. There was a lack of engagement, communication and urgency by all those who owed him a duty of care.”
She said her brother was a “kind, caring person” who “lost his life because of a number of missed chances by the mental health team, accommodation providers, the police, and the paramedics”.
A jury foreman told the inquest the officers' decision to use restraints was “inappropriate” because it was “not based on a balanced assessment of the risks to Mr Clarke, compared to the risk to the public and the police”.
He said: “It appears Mr Clarke was generally co-operative and responsive up until the point when officers laid hands on him.”
The foreman added: “It appears that the officers' decision to restrain Mr Clarke was unduly influenced by the knowledge that he had been Tasered on a previous occasion.
“They did not sufficiently take into account other facts that were clearly evident.”
The jury found the use of restraints was a “high-risk” option, which “escalated the situation to a medical emergency”.
“The restraint exacerbated Mr Clarke's agitation, leading him to struggle and causing him to become even more exhausted.
“Failure to properly supervise also meant opportunities to release the restraints were missed. It is therefore likely the restraint, and serious failures of supervision increased the risk of death more than minimally.”
Mr Clarke was moved to the ambulance while being “bent forward, with the back of his head held down by the hood” and his arms held in an “elevated” position, the inquest heard.
The jury said this “impaired his breathing and increased the stress on his body”.
It added: “Failure to remove all restraints at the point where Mr Clarke became unconscious was a further indication that speed was prioritised over his overall clinical needs.”
Mr Clarke had been living at the Jigsaw Project, a residential support service, for about two years up until his death in hospital on March 9 2018.
He had been seen by officers earlier that day, but was not sectioned despite concerns from staff at Jigsaw.
Police were called again later in the day and Mr Clarke was found lying on the ground at the edge of a school playing field.
An ambulance was called after the situation was deemed “a medical emergency”, and Mr Clarke was placed in two sets of handcuffs - linked together due to his size - along with leg restraints.
Pc Lee Pidgeon, who was one of several officers at the scene, told the inquest Mr Clarke had begun to get “a bit fidgety” and the use of handcuffs to restrain him was appropriate as he was showing signs of acute behavioural disorder.
In body-worn camera footage, Mr Clarke could be heard groaning, saying “I can't breathe” and “I'm going to die”.
When asked by coroner Andrew Harris why Mr Clarke was “ignored” by the officers in attendance, Pc Pidgeon replied: “I cannot answer that, sir, I don't know.”
The London Ambulance Service (LAS) has already admitted its crew failed to conduct a “complete clinical assessment” of Mr Clarke on arrival.
This amounted to a “failure to provide basic medical care”, which the jury said possibly contributed to his death as there was no “proper understanding of his condition”.
His cause of death was given as “acute behavioural disturbance, in a relapse of schizophrenia, leading to exhaustion and cardiac arrest, contributed to by restraint struggle and being walked”.
Commander Bas Javid, of frontline policing, said: “Firstly our thoughts and sympathies are of course with Mr Clarke's family and friends at this very difficult time. His death was a tragedy and on behalf of the Metropolitan Police Service, I apologise for the failings as identified by the jury.
“The officers who attended that day found themselves in a very difficult situation dealing with a man undergoing a mental health crisis who clearly needed urgent medical care. They made a rapid assessment and within 90 seconds had called for an ambulance.
“The Metropolitan Police Service is a learning organisation and we always strive to learn and improve. We continually review our policies in line with national guidance around restraint as well as how we assist those in mental health crisis.
“The jury has made several observations about how those officers dealt with Mr Clarke. Now we need to carefully consider those observations. We will work with colleagues nationally to consider our training and guidance to officers in dealing with these kinds of fast paced and challenging incidents. We will also in due course examine any further comments and reports by the coroner.”