If I remember correctly, I think it has something to do with a wife not being compelled to give testimony against her husband. At this point in the story, Will and his "wife" are not actually legally married -- because her previous husband had not died as had been assumed. But in 2 weeks (the waiting period necessary for marriage license or whatever ??), they WILL be married. It's something like that, I think. It's "obvious", isn't it (?)
