When does one become an accessory to murder?

http://wtop.com/local/2017/06/tooth-found-lyon-sisters-search-lost-bedford-co-sheriff/

Long time readers will know that this crime has been a major one in the DC region, and for all of my adult life.  I think that only the DC Sniper case has been bigger.  And to "lose" evidence in it is beyond believable to me.  No, you got rid of it, bubba, and you should be treated like the criminal that you are.  I am curious as to what a child predator could offer a sheriff in return for sabotaging a case....