I use to work at the DA's office where this case is on file. My last day there in Dec. 2007 I asked and was allowed to go through 4 boxes of files that were on the very top shelf in the file room. There are more boxes but they are housed at a different location across town so these 4 boxes is all that I saw but these 4 boxes included Grand Jury testimony, autopsy, field notes from Investigators, TX Rangers, photos,.....
Grand Jury testimony of the father-in-law is a joke. When asked simple questions such as his name his reply was "what do you mean?" or "I need to speak with my Attorney before answering." I AM NOT JOKING... After whispering with his Attorney he would answer with a question such as "do you want my full name including middle?" Meticulously detailed with his very short answers.
Personally knowing this family what I "think" is that it was a family argument over Shelley being out on the lake after dark on jet ski's, drunk & with a teenage niece, worrying everyone about their safety, a holiday where everyone was intoxicated at the lake house. One Jet Ski had run out of gas so one had to pull the other back to shore which is why they returned after dark. Family rule was no jet ski's after dark, this rule was mentioned quite often in Grand Jury testimony.
Once they returned and everyone realized they were safe, worry turned to anger. Maybe she was shoved and fell and hit her head....no way to truly know but I do feel it was an accident that the family then tried to cover up to protect the kids/wealth/name/status (your choice) in the community.
Shelley was a Rebel, haha,,, it is easy for me to picture her bucking other family rules and perhaps in their drunken state, animosity grew and other incidents were brought up and everything got out of control. I must mention that I do not feel that the father-in-law was present during the accidental death but was called after the fact and possibly the mastermind of the cover up along with the help of a veteran police officer.