They all died after police contact, but none of the officers involved has been suspended, and there are no official accounts of their deaths. Here, we reveal new testimony from bystanders

Darren Cumberbatch’s sister Carla could not remember him being so upbeat. Finally, he’d passed his driving test and was at last ready to fulfil his ambition of working full-time as an electrician. On 9 July – the last day on which anyone would recognise him as a healthy young man – Cumberbatch had called at Carla’s for a celebratory Sunday lunch, then spent several hours playing with her three children, who he cherished as much as his pitbulls: Bailey, Cream and their pup, Kaiser.

At 2.30pm a friend arrived and they visited a pub in Longford, north Coventry. “He was on top form, talking about the future,” said his friend Harvi, who did not want to give his surname. Cumberbatch was the only one in the group not drinking alcohol. The Coca-Cola he ordered cost £2.40 a pint – prompting friends to grumble about London prices creeping into the east Midlands.

At 5.30pm Cumberbatch took a taxi back to his bail hostel in Nuneaton. At 11.50pm Harvi missed a call from him. Shortly after, around midnight, Cumberbatch entered the room of a friend, Luke Purser, 25, for a chat. Purser said: “He was totally fine, he came in and gave me a cigarette, he was a very gentle guy, very nice, very soft. Ten minutes later the police came.”

No one knows who made the call to Warwickshire police that would determine Cumberbatch’s fate. Police records, though, reveal that officers were contacted by someone “concerned” about his behaviour. The official version of what happened next – from the police watchdog, the Independent Police Complaints Commission – states that the 32-year-old then “became unwell while the police were on the premises”.

New testimonies collected by the Observer suggest that the official version underplays the police’s role in Cumberbatch’s deterioration from the healthy and cheerful young man his friends describe to the person who would die days later in hospital having sustained a series of unexplained injuries.

Purser, from Birmingham, says that on that night a large number of officers entered McIntyre House bail hostel, where Cumberbatch had spent two months after serving a prison sentence for assault. Soon after, Cumberbatch was cornered in its downstairs toilet and seemed utterly bewildered, according to Purser. “The moment they entered they were shouting at him to get down. He wasn’t being threatening or aggressive, he was saying: ‘What have I done?’ He was scared, but they just kept shouting at him. They wouldn’t tell him what he was supposed to have done, then you could hear them Tasering him, again and again, then CS gas [spray], on and on.”

Another hostel resident Shaun Duffy, 54, said he “heard everything from start to finish, the police were on the go from the moment they entered. Shouting at him right away. They would use Taser and gas repetitively and without warning, there were no warnings. He kept asking: ‘What have I done?’”

Another witness, Vikash Shohan, 44, from Coventry, said: “You could hear the Taser noise near constantly, Darren was screaming.”

Duffy, Shohan and Purser all believe Tasers and an incapacitant gas were each used on Cumberbatch at least three times. On Friday, when questioned over the witness accounts, the IPCC confirmed for the first time it was not only investigating “police use of force” but the deployment of Tasers and the pepper spray PAVA.

Purser – who alleged that officers threatened to recall him to prison if he came any closer – also heard what he thought sounded like a beating. “I could hear the impacts,” he said, thumping his arm to mimic the sound. “Darren was going: ‘Aaargh, aargh, aaargh.’”

The IPCC’s chronology of events states that “shortly” after the police arrived, Cumberbatch was taken to a nearby hospital. Yet Duffy and Purser insist that Cumberbatch has been kept in the toilet by police for up to an hour. When eventually officers took him away, Purser watched from his upstairs bedroom window. “They were dragging him out, two officers, [holding him] each under his arms, his feet scraping along the floor. He was screaming for help, still asking: ‘What have I done?’ He looked scared.”

That was the last anybody heard of Cumberbatch for more than 65 hours. At 7pm on Wednesday, Carla received a call from Nuneaton’s George Eliot hospital revealing that her brother was an inpatient. When Carla visited him, his appearance stunned her – she said it was a “dramatic change”.

Unexplained bruises and burn marks were found across his body and feet. Neither the police nor the hospital have provided what she considers a cogent explanation for how he received such injuries.

The Rev Desmond Jaddoo, who is representing the family, said they wanted answers. “Darren’s appearance in no way reflected how he was when he left Carla’s house.

“Darren had bruising on his face, his hands, his legs, over much of his body, significant handcuff cuts into his wrists, burns on his body. There are also medical issues for which we are seeking answers.”

Cumberbatch’s condition deteriorated in the hospital and seven days after his sister was informed that he was there, he died

The alleged use of force and the fact that officers had taken him to hospital with apparent injuries, would normally warrant immediate referral to the IPCC. Yet it was 10 days after the incident that the police informed the watchdog – and only after Cumberbatch had died. The IPCC revealed last night it was investigating the “reasons for it not being referred sooner”.

Cumberbatch died at 4.25am on 19 July, one of three black men who lost their lives after contact with police in a period of eight days. All were restrained by officers, subsequently admitted to hospital and later died, apparently from related injuries. Four days after Cumberbatch’s death, footage from a supermarket in Hackney, east London, captured the moment a slim 20-year-old called Rashan Charles was pinned down by a Metropolitan police officer who had chased him into the shop after an attempted vehicle stop. About one hour later, Rashan was pronounced dead.

The previous weekend, Shane Bryant, 29, was restrained in a Leicestershire market town after a supermarket robbery. Bryant became “ill” and was taken to hospital, where he died two days later.

A month earlier, Edson da Costa, 25, was restrained by officers in Beckton, east London, after a vehicle stop. Again the official police watchdog says Da Costa, like Cumberbatch, “became unwell” after police contact. Da Costa was also taken to hospital and never recovered. In all four cases, despite post mortems and numerous tests, the families have still not been told the causes of death.

Facebook Twitter Pinterest The vigil preceding the funeral of Edson da Costa on the street in Beckton where Da Costa was restrained by police. Photograph: Antonio Olmos/The Observer

No officer has been suspended over any of the four deaths. What is viewed by some as an apparent lack of accountability has infuriated the families of the four men. “If it was any other public service they would have been suspended. It sends out the message that the death of a black person is not taken seriously,” said a representative of Rashan Charles’s family.

There is a sense among the families that justice might prove elusive. More than 500 black and ethnic minority individuals have died in suspicious circumstances in the UK while in state detention since 1990, analysis has found. Not a single official has been successfully prosecuted.

The IPCC is investigating all four cases amid misgivings over the transparency of its work. Compounding disquiet are concerns that the home secretary, Amber Rudd, is sitting on the findings of an independent inquiry into deaths in police custody, restraint and racial bias. A central component of the report asks why a disproportionate number of those who die after use of force are from black and minority ethnic communities. The report, which was to have been published a year ago, is now understood to have been completed and submitted to Rudd. There is still no date for its release.

“It’s quite appalling there’s been no explanation of the delays to families who have reservations about the fairness of the system. People are worried they are going to dilute the recommendations,” said Omar Khan of race equality thinktank the Runnymede Trust.

Pressure group Inquest has voiced concern that ingrained bigotry – institutional racism – is a contributing dynamic. Coincidentally, 10 days after Rashan’s death, Scotland Yard admitted using force disproportionately against black people. According to the Met’s data, more than a third of the 12,605 uses of force during April, May and June involved black individuals even though they account for only 13% of Londoners. The Met says force techniques prevent violence and protect officers, the public and the person being arrested.

For the IPCC, the four cases pose a challenge to its integrity. Low confidence in the watchdog’s ability has prompted Theresa May to announce that the body will be overhauled and renamed the Office for Police Conduct. The families of Cumberbatch, Da Costa, Charles and Bryant are among those hoping the rebranding is more than a PR exercise.

It was one of Da Costa’s preferred starts to a night out – stewed chicken and rice in Calabash, the popular Caribbean restaurant near Stratford Broadway in east London. Plus he had found a new song – D-Block Europe’s Traphouse – and when the 25-year-old had a fresh tune he was even more uproarious than usual.

“He was rapping, joking that we’ve got to get to the studio. I was going crazy with the Traphouse, telling him the next time I’m not okaying that song in the car,” said his friend Jussara Gomes, 23.

Just after 10pm on 15 June they were heading east on Tollgate Road in Beckton when the Mercedes A-class driven by Gomes was pulled over by officers driving an unmarked police car outside the Woodcocks estate. Plainclothes officers asked Da Costa to leave the car.

Gomes could hear them chatting for several minutes before sensing what she described as the “atmosphere” abruptly changing. Leaving the car she found Da Costa, who was wearing a blue Ralph Lauren tracksuit, lying on the ground. She said: “Edson was already on the floor, five steps from the car, face down. Two of them are already holding him down. Edson was moving but not kicking out or anything.“

Gomes said it looked like Da Costa had something in his mouth. “He’s not releasing whatever he has in his mouth so [an officer] pepper sprays him from really close.” said Gomes, raising her index fingers two inches apart to show how far she thought the CS gas was sprayed from his face.

“At this point I’m going: ‘Why are you guys still pepper spraying him if he’s already on the floor? His face was on the floor because I saw scratches after.”

Gomes said that after Da Costa was sprayed, he stopped moving. “I was asking: ‘Why is he not moving? He’s not reacting, not moving.’ This is all I’ve said for five minutes. All of a sudden, foam started coming out of his mouth. That’s when they stopped holding him down.”

By now, other people from the estate had come to see what the pandemonium was about. One of the first on the scene was David O’Brien, who lives 10 yards from where Da Costa was being held. “My son had called to say there’s an incident happening outside and I went out to see three officers – two were on top of him, one was trying to get people away.”

Facebook Twitter Pinterest David O’Brien, who witnessed the incident that preceded Edson da Costa’s death, at the place where it happened. Photograph: Antonio Olmos/The Observer

O’Brien said when he arrived at the scene, Da Costa seemed wholly passive. “There was no need for them to be on him, he wasn’t struggling, he wasn’t resisting arrest whatsoever.

“But he must have had difficulty breathing with the two officers on him, their weight crushing down on his chest and his face on the floor.”

O’Brien estimated that the officers might have been on top of Da Costa for up to 10 minutes. He said Da Costa then appeared to stop moving and for five or six minutes seemed “lifeless”.

O’Brien said he then began to fear for Da Costa’s safety and started screaming at the officers to get medical help immediately. “He wasn’t moving, I started shouting at the officers to call an ambulance.”

The witness said Da Costa’s condition seemed to deteriorate. “He wasn’t breathing. I was saying, ‘Call an ambulance.’ He had stopped breathing. Then they rolled him over and started trying to resuscitate him.” O’Brien believes it was too late. “They tried to resuscitate him for 10 minutes, but he was already dead. His chest wasn’t moving, he had stopped breathing. His chest was flat. He was totally lifeless. I watched him die in front of me. He died on the street, definitely. Everyone will tell you that.”

Student midwife Samiya, who lives next door to O’Brien, went outside after hearing a commotion. “I heard screams of: ‘Get off him, get off him, he’s not breathing.’ It was hysterical.”

Samiya, who managed to get extremely close, said that from her experience, it looked like Da Costa was dead. “His skin was grey, it had lost all its colour. He looked nothing like he does in his pictures.

“When I turned up they were giving [him] CPR [cardiopulmonary resuscitation], but he looked lifeless, like he was gone. They were giving CPR but he wasn’t responding.”

She saw paramedics still administering CPR to Da Costa in the ambulance.

Another neighbour, Lee Hulme, recalled hearing frenzied shouting outside between 10pm and 10.30pm. “A man was shouting: ‘You’re killing him, you’re killing him.’ That must been over the space of 10 to 15 minutes.”

Several witnesses also told the Observer how they were both mystified and repulsed that Da Costa had been undressed. “I couldn’t understand why he was butt naked. They had taken all his clothes off, socks, trainers, everything. There wasn’t a scrap of clothing on him,” said Samiya.

O’Brien added: “They took all his clothes, he was totally naked. They took away his dignity. Why would you take off a man’s trousers in front of all those people?” Hulme, who lives 30 yards from where Da Costa was arrested, said: “He was stark naked on the floor, naked and lifeless.”

Da Costa was taken to Newham general hospital but never recovered from his injuries. On 21 June, six days after being admitted to hospital, the father-of-one’s life support was turned off. He died in the presence of 70 family members and friends. On Friday, scores congregated for his funeral at Manor Park cemetery, three miles north of the street where some believe Da Costa, who hoped to set up a car refurbishing company, had actually died before being taken to hospital.

The IPPC, meanwhile, continues to examine “the use of force, as well as the subsequent response in administering medical assistance”, to Da Costa. It has confirmed CS spray was used on him. Official guidance on the use of pepper spray has, in the past, indicated it should not be used at a “distance of less than one metre”. The guidance states that officers need to be aware of appropriate restraint positions after spraying a suspect.

Elsewhere, the advice is less clear. Despite other deaths that have occurred in similar circumstances to Da Costa’s – and at least one warning from a coroner this year – there is still no official guidance for police facing someone who has swallowed a package. Similarly, no national direction exists about whether pepper spray should be deployed if someone is believed to have placed something in their mouth.

It lasts less than four minutes – three minutes and 53 seconds – but the video is long enough to show a seemingly healthy Rashan Charles in obvious distress. The footage opens with the slender man walking into Yours Locally, a late-night supermarket on Hackney’s Kingsland Road. The 20-year-old Charles was familar with the shop as he had grown up around the corner.

Moments later, just after 1.45am, a uniformed officer follows him inside after an attempted stop of a vehicle in which Charles was a passenger. The officer quickly wrestles Charles heavily to the floor. The images, taken from inside the shop doorway and used with permission from Charles’s family, show the officer attempting to prise something from Charles’s mouth. There does not appear to be any threat from Charles, who is seen squirming beneath the officer as an onlooker watches.

Things change at the one minute, 13 second mark on the video when a member of the public wearing jeans and a hooded sweatshirt assists the officer by climbing on top of Charles. The officer than handcuffs Charles’s hands behind his back while he continues to be held face down.

On the video, at around the two minute, 30 second mark, Charles appears to have stopped moving, his face still on the floor, the full weight of the other man on his back. The officer checks Charles’s mouth. Just before the three minute mark on the video, the officer is seen removing his own cap and uses his radio. Charles still does not appear to be moving. At three minutes, 50 seconds, a female police officer hurridly enters and kneels beside Charles. The video stops.

“Losing your son is the hardest thing, but like that is unbearable,” said a family friend, who requested anonymity. What happens next, according to the IPCC, is that a police medic and paramedics attempt to save Charles’s life, though he is recorded as being “unresponsive” on arrival at the Royal London hospital, Whitechapel. Charles was confirmed dead at 2.55am.

A statement from Scotland Yard the following day suggested that the officer had “intervened and sought to prevent [Charles] from harming himself”. Forensic tests later revealed he had tried to swallow a mixture of paracetamol and caffeine wrapped in plastic.

The family are keen to know the identity of the man who helped restrain Charles. The IPCC has confirmed it has interviewed him.

Facebook Twitter Pinterest Diane Abbott, the shadow home secretary, speaks at the Justice for Rashan Charles vigil outside Stoke Newington police station in London on 29 July. Photograph: Emerson Utracik/Rex/Shutterstock

The IPCC investigation will, like others, attempt to knit together the chronology of events while examining “what police guidelines say should happen in these circumstances”.

One potentially significant document is the Met’s standard operating protocols for officer safety training. It has a section titled “clear considerations for safer restraint” with particular detail devoted to “positional asphyxia” – ostensibly, how the body’s positioning can interfere with breathing.

The document, drawn up by CO11, the Met’s officer safety policy unit, warns positional asphyxia can occur “extremely rapidly” and lists several factors that “can contribute to death” including if “pressure is applied to the back of a person held in the face-down prone position”. To reduce the risk, the document, reviewed by the Met in July 2014 and released under freedom of information, urges against placing anyone face down and warns the onset of medical complications can be “seconds not minutes”.

The weekend before Charles’s death, father-of-two Shane Bryant, 29, from Birmingham, was restrained after a robbery at a Co-op in the Leicestershire town of Ashby. Bryant was detained by members of the public, including an off-duty Leicestershire police officer, until other officers arrived. Like Da Costa, Bryant “fell ill” on the street and was then resuscitated by paramedics for a lengthy period. One witness reportedly said life-saving attempts lasted 15 minutes. He was taken to hospital and died two days later.

Four deaths, all different, but with sufficient similarities for some to suggest a pattern. Yet the new details form only part of the narrative – the testimony of officers involved is not known – and the IPCC investigations will take months to conclude. Both the Met and Warwickshire police state that only when the watchdog has established the full facts can “any conclusions be made”.

Yet the deaths pose awkward questions for the police, fermenting simmering disquiet over longstanding issues of race and criminality. All four families want the truth, then justice.

Speaking in the vast gloom of Coventry Cathedral, Carla Cumberbatch believes police accountability is imperative. “Don’t single out people for special treatment – and here special treatment appears to have been dished out. We want those that dished it out held responsible.”