Why would any district attorney or police chief hesitate to file criminal charges against an officer who used an UNAUTHORIZED tactic that

I would hope it has more to do with creating an airtight case than anything else. I know sometimes they'll gather evidence in the background or piece things together when they don't think the suspect is going to run. If that's what was happening- them making sure things were handled 100% by the book and methodically to ensure justice is served- I can respect it. If it was anything else... I don't know. Maybe they were waiting for autopsy results as well to determine what charge it would be?

The justice system we have today has been allowed to infect itself with corruption, bias and cover up's.  It is more than police not treating people of color fairly it includes the attorneys and judges who manufacture evidence to make sure their "city" is always blameless.  It is everyone's problem not just people of color.  The poor who cannot afford an attorney and have to rely on a public defender who has more cases than any man or woman could handle and do it well.  Every time an innocent man or woman pleads guilty just to make it "all go away," or who really have no choice, the injustice in our system digs its heels in deeper and deeper.  The fox is watching the henhouse, there is no accountability outside of the corrupt system itself.  We need another amendment to the constitution that mandates how our justice system should work.  We already have all the elements now we just need a clear, simple, and fair way to implement what we already have across all states. 

I have no idea. They maybe building a case so the murdering cops do not get off on a technicality.  That would be even worse. 

I think there should be a separate agency that handles cases against the police/FBI/etc.  And a separate procecutor specifically for them.  Penalties for commiting a offense as a officer of the law should be stronger than normal people. We should expect more from our officers...we trust them with a badge and a gun to protect the people of this country.   
Procecutors rely on police to make their case against criminals. If they prove one is dirty, it can threaten every case they have used the officer as a witness. Leading to a conflict of interest in deciding if/when to prosecute a dirty cop. 

Maybe use miliary JAG investigators/attorneys? 

Cops policing cops....does not work. 

not sure why