Justice delay can be justice denied.
In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial ...Today's trial process are way too long, partly because jurors acted like lynch mobs in too many cases. Under the ideals of the Founders "Justice" didn't mean someone got the noose because someone else was murdered.
Under those IDEALS, which are great, it is more likely that a murderer would walk free, because in many cases there is only circumstantial evidence, or unreliable witnesses.
That's NOT enough to get beyond "reasonable doubt".
To get beyond reasonable doubt you need reliable DIRECT witnesses. In terms of evidence, you need a whole lot. A lot more than has been presented in most murder trials I remember.
But the Founders understood JUSTICE better. In the end Justice is in the realm of the Divine. Men can only do their best, and be utterly honest, in pursuing it.
No murderer ever really walks free, G-d has taken account and that account will be settled.
In this case the injustice is that until that cop is tried for the murder, the possibility of that charge coming up later will ever hang over him and hobble him, and prevent his soul's desire for Justice in this world--for a SPEEDY trial resolution in this world of men, from being settled. It is like an open sore on his soul.
It's the same for those close to the murdered man. Their souls too cry for a settling of the accounts of Justice.
Such open sores of trials not held by a society are festering wounds to the society. Better to have a trial and have the officer walk. That partially heals the social wound, even if he did do the murder.
Even though, like I said, it looks like it was cold blooded murder to me.