Malgus, you are missing the point.

The same DAs office has set precedent previously by prosecuting these cases, their sudden flip flop because of the lynch mob will make the situation untenable and possibly invalidate any prosecution

Actually the blame and liability would fall on the department if the training was faulty and/or incorrect.

Your nazi comparison is hardly appropriate, but expected.
In this instance its more akin to the city fathers of Tombstone saying people couldn’t wear guns in town all those years ago.

No setting precedent is not retroactive, you should understand that.
Much like the Commiefornia SKS ban where they changed their minds and made the now registered SKS’ s illegal retroactively. However those actions may set a precedent for future legal actions.