I dont think Tom knew about the paving stone. It is interesting that notwithstanding the risk of us all unduly influencing each other there seems an overwhelming belief that Molly was the main protagonist in this crime and Tom played a supporting role. Why is that I wonder? Is it because of the facebook campaign and Molly's actions subsequent to the murder, or is it evidence based? I personally think it is because, assuming we dont believe the self defence theory, TM didnt have enough motive to kill as MM did, and with two weapons there were likely to be two assailants. But we really have to ask ourselves, given that TM said he alone did it, and not withstanding that a Grand Jury indicted them both, why do WE think MM is the main protagonist? I dont think we are wrong, but I think it may move our thinking forward if we consider why, predjudices aside, we believe we are so right?