Half way into saw 3 I realized john knew about Hoffman's note to Amanda, could he a possible known about the context of the letter, or informed hoffman to write the letter to give Amanda a choice of whether she would follow through on the plans or murder an innocent person to protect her secret? He also must've known hoffman wrote it since we know he was there right before amanda, and he was bed ridden since even before the movie so there's no way he could walk across the plant, to his desk to know about the letter. I think this also puts another emphasis on the last words john exchanged with Amanda, because he didn't want to believe it, but she was just a full fledged murderer who was also responsible for the "murder" of his unborn son. If true, it adds a whole new dimension into how Amanda was being tested and the saw 3 plot.