FBI stupid mistakes

I am no law enforcement officer or attorney, but if they charged the Sheriff (like Skylar so wanted to), I could get the charges thrown out of court in 5 minutes flat. Seriously!! First of all, the evidence against him was circumstantial at best. He had no connections with the previous 23, yes thats right 23 victims. Finding one of his hairs in a place his niece was known to be cannot be viewed as definte proof either! She is his niece. Maybe he hugged her, was in her car at some point. So easy for hair to be transferred.
Surely the FBI knows this!!!!