Big problem in cases like this is proving 'who did it ' - 10 people can't all be charged with murder, so if they keep quiet and refuse to confess the investigation goes nowhere...
Me - I would send them all down for life , but it ain't up to me.
Has as been mentioned elsewhere the law of Joint Enterprise allows a whole group of people involved in a crime to be charged with it.
This does not only apply to murder cases.
Sometimes the Police are able to get more evidence about a crime when one of the group provides evidence to prevent being charged.
Talking to a friend in the Police he tells me it works but is only used in serious cases where substantial sentences are likely to be given.
I hope that if someone is found guilty of this crime the judge will take into account the murdered man was a policeman. In addition to a heavy sentence the judge can also recommend a minimum length of time the convicted person should serve before release is considered.