Exclusive: Campaigners say calls to redraw rules are cynical attempt to secure ‘effective immunity’ for officers

Police chiefs have formally asked the government to make it harder to investigate and prosecute officers after the fatal shooting of Chris Kaba led to a Scotland Yard sergeant being acquitted of murder, the Guardian has learned.

Campaigners have criticised the move, saying calls to redraw the rules were a cynical attempt by police leaders to secure “effective immunity” for their officers.

Making it harder for the Crown Prosecution Service to charge officers, with police chiefs proposing prosecutors would have to prove training or approved professional practice was not being followed before taking action.

Changing the standard of proof required for a verdict of unlawful killing ahead of the inquest into Kaba expected as early as next year. Currently the ruling is made on a balance of probabilities, the civil standard. Police chiefs want it to be the criminal standard, which is beyond reasonable doubt.

Making it harder to disprove a claim of self-defence in misconduct inquiries, by changing the standard to the higher criminal test, rather than the current civil test.