IANAL, but I have spoken to them, and had them in my (extended) family.
One thing stands out - more than one has told me that if instead of the Miranda warning police were required to slap a piece of duct tape over the suspect's mouth until his attorney arrived, convictions would plummet by well over 50%.
In the absence of some evidence - continuous video, admission of guilt, bragging on Facebook,
something tangible - there won't be any successful prosecution for prior illegal concealed carry based on mere
assumptions and
inferences by the DA or police.
Oh, and Bernie Goetz was mentioned . . . who HASN'T seen the videos of him referring to himself as a "rat" during police interrogation? As it was, IIRC, he was only convicted of illegal gun possession in NYC; one wonders what the outcome would have been had he shut his pie hole from the beginning.
In some places, police have a policy (not law, but a policy) of ignoring illegal carry in the event of a "good shoot".
I've heard of some cases where police ignored illegal concealed carry - no arrest, person sent on their way with their gun, no record of the event - but not after a shooting. I've also heard that in some shootings, the police, well, they don't look very hard for the shooter. But regardless of jurisdiction, it's not something to rely on.