'American Idol' Reject William Hung -- Now Dropping Hits ... With the Sheriff

William Hung can still draw an audience -- nearly 8 years after murdering "She Bangs" on "American Idol" ... he's landed a sweet gig in law enforcement, of all places.

TMZ has learned Hung is now working for the L.A. County Sheriff's Department as a Technical Crime Analyst -- fancy name for a dude who crunches numbers to help prevent future crimes.

Just last week, William dropped some knowledge (above) at a training facility. Communication was always his strength.