Being a former Wildlife Agency employee myself, I am enjoying this discussion. As far as using DNA, fish biologist are constantly using DNA in their work, and I don't mean law enforcement, but in trying to study the populations of fish in various drainages. It sounds like they used some of that research to try and convince a judge the guy caught his fish in the wrong lake, but the judge didn't buy into it.
BTW, wildlife LEOS, like anyone else, do have to earn their respect. The attitude that just being an LEO means people have to respect you is a mistaken attitude. It is still supposedly a free country and anyone has a right to express an opinion, especially regarding the actions of public service employees. That also doesn't mean all criticism is right. A lot of it is misguided due to lack of being privy to all the facts. Some of it is well guided, though. It's one of those, "if the shoe fits, wear it" situations. If it doesn't fit, don't worry about it, IMHO.