Although I have been following this forum I am a first time poster I have always been very interested in the case as my daughter attended Girls Grammar at the same time as Allison and they met up less than 12 months before her murder at a school reunion.I have been thinking about the marks on GBC chest and thought the one under his armpit could be caused from someone grabbing his shirt with force pulling it up under his armpit or Allison grabbing it from the front with force and pulling it up try it yourself it is possible and it does leave a mark.