The decision not to prosecute any police officer for the shooting of Harry Stanley fits an alarming pattern for such cases.
Of 30 fatalities involving police shootings in the past 12 years no officer has been convicted of murder or manslaughter.
Daniel Machover, the solicitor representing the Stanley family, said there was a real concern that the Crown Prosecution Service had set the evidential bar too high when it came to considering charges against police officers. He said police need only raise a prima facie defence of self-defence to block prospects of a successful prosecution.
Lawyers are also concerned that the prosecutors and the Independent Police Complaints Commission, which initially investigates these cases, have become unduly influenced by American experts in the field of ballistic biomechanics, the study of human reaction times and body movement in relation to firearms incidents.
An American expert was relied on to help support the officers' accounts of the Stanley shooting and refute the allegation that the decision to shoot was taken after Mr Stanley had turned away from the police.
This science, which has not been properly tested in British courts, is used extensively in America to help clear US police officers of homicide offences.
Under UK police guidelines, officers are allowed to discharge their weapons to defend themselves or protect members of the public whose lives are threatened. The guidance makes clear they should "shoot to incapacitate" and shots should be directed into the upper body to try to shut down the central nervous system as quickly as possible.
But since the shooting of Jean Charles de Menezes, this policy has been adapted to face the threat from suicide bombers. Senior officers believe using "shoot to incapacitate" gives the bomber time to detonate a device, for example by clicking a button, even after they had been shot. Also it was feared shots to the chest area could trigger a strapped-on device. The Association of Chief Police Officers insists there has been no change in the law or in firearms policy.
Investigations into police shootings are initially led by the IPPC which oversees a team of senior investigating officers. The IPPC liaises closely with the CPS and will recommend to prosecutors whether there should be a criminal prosecution. The CPS makes its own decision independently on the twin criteria of public interest and sufficiency of evidence.
In police shootings, the Director of Public Prosecutions will confirm the decision and may pass the file to the Attorney General who has cabinet responsibility for the CPS. In his constitutional role as superintendent of prosecutions, the Attorney General can only be consulted by the DPP about high-profile cases. His role will face scrutiny when the CPS decide whether the shooting of Jean Charles de Menezes should lead to criminal prosecutions.
Only when the decision not to prosecute has been taken will a full inquest begin. In the past 12 years there has only been one finding of unlawful killing and that was in the case of Harry Stanley. The High Court overturned the verdict, prompting protest from the Stanley family.
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