Yes!  There are numerous, reliable reports of people decapitating snakes, picking up the heads, and being bitten.  Once the head is separated from the spine, the brain continues to send nerve impulses, resulting in muscle spasms.  One of these muscle spasms can easily manifest itself in the snake's mouth, resulting in a bite for the unsuspecting person holding it.  Thses spasms have been recorded to continue for up to one hour after the snake has been killed.