What does a bailiff say when he swear s in a witness?

It can vary from state-to-state - and in many states it is not the Bailiff that does the swearing-in. In some states it is the Clerk of the Court that does the swearing-in, and in still others the judge themself handles the job. The actual Words go something like, "Do you swear to tell the truth, the whole truth and nothing but the truth, so help you?" Fewer and fewer court systems (if any) use a Bible for swearing in wtinesses any longer, or use the Words, "so help you God.'