I'm really concerned about this, too. A few days ago, I wondered why nothing is ever said about the autopsy reports for JJ and Tylee, let alone Tammy's.
Others have mentioned that there have been no charges in regard to Tammy, so why would Defense think they had a right to that report?
Same with JJ and Tylee. Defense will not see the autopsy results unless and until murder charges are brought against Chad and Lori. And unless those reports link Chad and/or Lori to the deaths of those children, we may never know. Seems like they do not have the evidence to charge them, at least at this time.