Having sex with a cop in uniform is one of the oldest fantasies in the book.
If the cop involved is an actual on-duty sheriff's deputy, however, there are several rules that need to be abided by. First and foremost: don't leave the radio to dispatch on while you're getting busy.
Source:
http://blogs.seattleweekly.com/dailyweekly/2010/11/sherriffs_deputy_may_have_left.php