I have no idea what book or story you are talking about, but based on my knowledge of Law... asking a person the same question over and over and cause a reaction in their fight or flight extinct, the person will start to become worried and they'll either start changing their answer or they'll break down completely. I'm guessing the when Hathorne asked the same question several times to Sarah, she started to get nervous.
I hope this kinda helped
Well assuming you mean America, and not considering Civil War, I would say the draft of the Constitution Thomas Jefferson want to make slavery illegal, but he needed the southern states approval.