This is one situation where I think the US could take something of value from the English judicial system. In England even a legitimate shooting by the police would result in a coroners court enquiry into the circumstances of the death (as are all 'unnatural deaths e.g. RTA). The police involved would be called to give evidence under oath. The postal inspector could be called. Documents would have been made available. The families lawyer, or the judge on behalf of the family could put questions to the supervising officer etc. The jury would return a verdict likely justified homicide. The coroner could issue and the jury could recommend certain actions be taken by the police to prevent similar circumstances occurring in future. All this in a public court. The problem with Grand juries (which is surprising in the US) is that they are secret. In general the process of justice should be open not secret.
If every police fatal shooting was subject to judicial review (and equally every fatal shooting of a police officer) I think improvements in policy would have happened. It also makes it easier to amend law as judicial recommendations can be seen as less political and so easier to gain bipartisan support than if they are brought forward by one party. (I realise that the US has politicised its judicial system, unlike the rest of the common law world, so this is less true in the US.)
