In the wild west, a Colt single-action revolver was known as “the peacemaker”. The Metropolitan police commissioner, Cressida Dick, hopes for the same effect by proposing to deploy armed officers on foot patrol in areas plagued by knife crime and other violence. But might this make a bad situation worse?

The need for trust is essential for the social contract of policing by consent to be effective. Despite fictional accounts of heroic detectives, most crimes are solved by the public providing vital information. The need for families and friends to trust police to respond effectively and appropriately is key.

But, like friendship, such trust cannot be achieved quickly. It takes time to overcome mutual suspicions and collective memories of cultural, political and media antagonism. For some communities, the police are seen as occupying armies. For some police officers raised in places with few or no members of ethnic minorities, their views are based on war stories about hard times on the streets. Police often feel nobody appreciates them or their role as the thin blue line against disorder and violence.

What’s more, police are only human. They make mistakes. When firearms are involved, they can be fatal. In the 80s, when guns were handed out more freely, Stephen Waldorf, a film editor, was shot repeatedly in west London in mid afternoon because he looked like an escaped prisoner. He was severely injured but survived. The case led to restrictions on the use of firearms.

More important still was the case of Cherry Groce, the mother of someone suspected of having a firearm. The police raid on her house in 1985 by exhausted officers led to them shooting her and leaving her paralysed. The riot that ensued was the second in four years in Brixton, in south London, with devastating consequences for the area and for police and public trust.

We could look to the United States for a warning. Lethal police mistakes there come to our attention with terrifying regularity. On Friday, the Dallas police officer who shot an unarmed black man in his own flat because she thought it was hers was finally indicted for manslaughter. This is rare in the US, where simply a fear of being threatened is accepted as justification for killing unarmed people.

In London, that verdict prompted rioting after the officer who shot Mark Duggan in Tottenham in 2011 was acquitted, despite the weapon being found yards from the vehicle in which he was in.

Respect for the whole criminal justice system is affected by such events; it can reflect deep mistrust between the ethnic-minority communities and the police, made worse by harsh economic conditions. In this context, another new Met policy of addressing moped robberies by knocking riders to the ground could have fatal consequences.

Facebook Twitter Pinterest Cherry Groce was paralysed from the waist down after being shot by police searching her home in Brixton in 1985. Photograph: PA/PA Archive/Press Association Images

For supporters of tough policing, such events are merely collateral damage against a rising tide of lawlessness on our streets. But for communities used to decades of police harassment, each such incident symbolises what is seen as an abuse of power. It sets back genuine police efforts to improve public trust.

The return of what is known as “slow rioting”, in which police cars are attacked by crowds of young people, is a worrying indication of the current attitude towards police among that age group. They are most vulnerable to violence because they are on the streets more than the rest of us. A crowd of youths attacking Durham police trying to help a girl at a bus stop has gone viral and will worry police around the country as well as the rest of us.

Crime prevention has never been valued in police culture as much as crime fighting

The Brixton riots led to the creation of community policing to address deeper causes of unrest. But crime prevention has never been valued in police culture as much as crime fighting, known as “real” policing. Feeling collars or subduing violent offenders makes better stories than a quiet time on the beat or finding lost old ladies.

Yet consistently low detection and conviction rates show that crime is not their strongest suit. What police are good at is solving problems. This is a major resource in terms of building local trust.

In the aftermath of riots on the Meadow Well estate in North Shields, in North Tyneside in 1991, the chief constable assigned a sergeant and 12 PCs to an economically deprived estate that was deeply suspicious of the police.

The sergeant, Alan Evans, sent his PCs house to house to ask what they could do to help them. Initial suspicions gave way to genuine trust, which led to flows of intelligence that helped reduce crime. Some parents even turned in their own children in the hope that police could save them from a life of crime.

There were two interesting outcomes from that experiment. The other officers in North Shields regarded the volunteer PCs as traitors. And the neighbouring New York estate asked: do we have to burn ourselves down to get the same level of service?

But problem-oriented policing has never been properly valued by politicians either, partly because it cannot be counted in key performance indicators – “the stick with which to beat the police”, as one home secretary described it to me.

In fact, politics is having severe consequences for police and public relations. Police numbers and budgets have been cut radically, while demand for them to do more about a wide range of crimes such as domestic and sexual violence, people-trafficking and fraud has risen exponentially. Governmental denial about the impact of cuts on policing is not only misguided. It fails to recognise how youth crime is affected by the closure of local authority support: from Sure Start to youth clubs and other resources to provide refuge.

The need for a joined-up approach to crime and its causes has long been recognised more in the breach than in the observance. Until, and unless, resources are found to restore community policing, to provide legal aid for those caught up in the justice system, and for prison officers to do more than lock people up for most of every day, the criminal justice system is at risk of creating more damage than it prevents. Roger Graef is a filmmaker and criminologist