Allowing someone not certified to do the work is a pretty big no-no for a regulated profession. It's bad enough if a contractor allows their untrained buddy to work on your sink, but this is about criminal investigations, someone's liberty at stake. Not only would any investigation that uncertified deputy was involved in be thrown out of court, but the sheriff rightly was looking at possible decertification himself, hence why this was all public. Certification is necessary for a reason and the stakes don't get much higher than criminal investigations. The state takes it quite seriously.

Edit: And if he's this sloppy about serious matters like this, where else is he sloppy? What else is he allowing? Just a horrid look for a sheriff.