Divedoggie,
Thanks for your responses and I agree with much of what you are saying. You sound like a conscientious instructor. Your conclusions on how to prevent this kind of accident happening are along the same lines as McFadyen's and I suspect others on the board.
As mentioned previously, I thought your comment about breathing around the regulator when students are panicked was a breakthrough in my own thinking on the topic and sounded a plausible explanation. I was interested to hear from McFadyen if that came up in the discussions with the defense team and other alternative explanations that surfaced.
Oh and have to say that your perspective from the point of view of an instructor was helpful in gaining a lot more insight into what happened. So again thanks.
Foxfish,
Thank you for your insight and participation as well. Your comments have been inspired and enlightening. It has been a pleasure to get to know you and others on this thread.
The 'breathing around the regulator' scenario may or may not be what happened to Tina, but I have seen the phenomenon several times. I'm really pleased that it sparked a breakthrough in your thinking. It was not a stroke of genius on my part, just observation. In addition to the story that I shared about it, a woman who is a friend of mine had this problem during training in the pool. We had to try 4 different mouthpieces before we found one that worked for her and allowed her to seal her lips around it. (She ended up using an aqualung comfo-bite mouthpiece.)
We all discussed another possibility a ways back, as well. Tina may have breathed irregularly, panting through the reg which could have caused Hypercapnia and in turn she passed out. The reg would have been in her mouth, but as she lost consciousness, her lips relaxed and she breathed water around the reg. Again, being found at the bottom with the reg in her mouth is explained.
Students grab the SPG or the snorkel instead of the low pressure inflator. They also press the wrong buttons, or don't press them hard enough, or long enough, or too long. They get caught up in pressing buttons instead of controlling buoyancy.
There are just so many things that inexperienced divers may do wrong, it get away with, because an attentive DM, Instructor or buddy was nearby.
I'm also looking forward to McFadyen's report.