Marcia Rigg compared officers in this country using their ‘bare hands’ in incidents lasting minutes to American officers making a ‘split second’ decision before shooting people.

Her brother Sean Rigg, 40, died in police custody in 2008 after being restrained by officers for at least seven minutes. Five Metropolitan Police officers were cleared of misconduct last year, more than a decade after the musician – who had schizophrenia – died.

Marcia believes her brother would have said the words ‘I can’t breathe’ as he was restrained in Brixton, south London, in similar circumstances to George Floyd, whose murder in the US sparked a global movement against racism and police brutality.

Speaking exclusively to Metro.co.uk, she said: ‘It is worse here. I went to America back in 2015 and met some of the families [of those killed in custody] and they could not believe that most officers in this country do not carry guns. I told them they use their bare hands, they were horrified.

‘That is how George Floyd died but most of the deaths are by gunshot, which takes a split second.’

She added: ‘It takes a second to shoot somebody but the fact that you can use unnecessary body weight on somebody at the neck or chokeholds for X amount of minutes is really something else.’

Yesterday Wayne McDonald – the brother of a man who was restrained before his death in the back of a police van in 2014 – told Metro.co.uk it is a ‘shame’ that it took the death of a black man in America for Brits to understand the scale of the issue in the UK. According to the charity Inquest, 1,744 deaths have been recorded in police custody in England and Wales since 1990. No officers have been convicted over the deaths, which have a number of different causes.

Criminology lecturer Dr David Baker, an expert on police brutality, told Metro.co.uk: ‘We are fooling ourselves here if we don’t think it is a major issue too. We hold our police up as being somehow better (than in the US) because it fits with the national myth we have of ourselves.’

He claimed it is ‘really difficult’ to believe police testimonies because there are ‘so many cases’ where it has ‘fallen apart’ under examination in court – whereas in the US there has been a history of convictions.

Marcia believes there are similarities between the two countries, notably in autopsies highlighting underlying health conditions that she believes shifts some of the focus away from the contribution of police restraint at inquests.

Raising the case of George Floyd, she said: ‘They always say that a person was in custody, that they became unwell and died. But the “unwell” bit is the restraint. So what they are trying to find out first is “do they have a bad heart or any other medical issues?” to try to say that they died with that.

‘Only when it happens to you personally as a family, do you realise that this happens.’

She added: ‘The first time I saw the video [of George Floyd’s death] I could just think of Sean, because that is how he died.

‘When I saw that video and other deaths like that in the past… I believe my brother would have uttered the words “I cannot breathe” – I believe he must have said that. The fact that the officers didn’t show any care whatsoever is exactly what happened to my brother.’

Marcia said the protests in recent weeks are ‘important’ and encourages the use of social media to share videos of incidents of police violence, arguing officers must not be able to act ‘with impunity’.

In order for the situation to change, the government must have a ‘political, moral will’ to make it happen, she said.

‘What we want is a conviction because that is when it will send a clear message to officers. We have recommendations after recommendations, we have got so many reports. But they don’t implement them. Why?

‘(They say) “lessons will be learnt”. What lessons? What training do you need to know that if you restrain someone for X amount of minutes they are going to die? If you put a pillow over somebody’s head for X amount of minutes you are deliberately doing it, you are going down for murder. Why can’t a police officer?’

Dr Baker, who works at Liverpool University, called for ‘some sort of agency’ to analyse deaths in custody independently and for the current organisations involved to talk to each other.

The Independent Office for Police Conduct (IOPC), which currently looks into deaths, said its role is to ‘thoroughly investigate the circumstances’ and then refer it to the Crown Prosecution Service ‘where the evidence suggests criminality’.

A spokeswoman said: ‘We always refer matters to the CPS where there is sufficient evidence. The CPS decides whether a prosecution goes ahead and, when it does, only a jury can make the decision to convict a police officer.’

She added: ‘Now more than ever we need to strengthen, not weaken, police accountability.’

The Home Office is currently ‘exploring’ alternative methods of restraint following the Independent Review of Deaths and Serious Incidents in Police Custody.

A spokesperson said: ‘Every death in police custody is a tragedy and we recognise how devastating they are for families and friends – they are always thoroughly investigated by the Independent Office for Police Conduct.’

In a statement, the Metropolitan Police said Mr Rigg’s death ‘has always been a matter of regret for the Met along with the additional stress suffered by both the Rigg family and the officers involved caused by the delay in bringing matters to a more timely conclusion.

‘We are pleased the Rigg family are also working closely with us to improve our public misconduct hearing processes as well as the Met response in general to those suffering mental ill-health.’

The National Police Chiefs’ Council says it is developing a ‘plan of action looking at issues of diversity and inclusion and concerns about racial inequalities in policing and the criminal justice system’.