First, with regard to seeing Shelley and her fin. If it was so obvious and right along the path, then Thwaites would have seen it before ever reaching the bottom in this great visibility that you all describe. Or, maybe the mooring line isn't where you are assuming it to be relative to the wrecks and reef?
The pictures I posted earlier should help to visualize the dive site and the layout of distances between the anchor line, the wrecks, the fin and the reef. Who is to say that Thwaites did not see the fin before reaching the bottom? The jury would question first why Swain did not see the fin when Thwaites did see the fin before they would pose the question you are posing.
As far as the staging of the scene goes, I'm not sure how anyone would think that sticking a fin into the sand 30' away from the body would give the impression of panic. It certainly wouldn't suggest that to me. Would you finish killing your wife and then take off her fin, swim 30' away and stick it into the sand as a means of suggesting she had an accident? Ever hear of an accident that happened like that in calm clear water? I bet David had heard of or even experienced a few diving accidents in his years as an instructor and shop owner. You would think he'd be able to construct a more believable accident scene if he were so inclined. Maybe even left her snagged on the wreck or with her body sticking into some compartment.
Staging certainly would cause confusion with any investigation and I would venture to guess that most people who commit murder will quickly react to change the evidence in some way to create confusion so that evidence does not remain intact in its original state. The scenarios that you come up with to stage a better murder may not be the same scenarios that someone else would come up with. Staging her inside the wreck is too specific and attempts to create to much detail to in order for the investigation to come up with a particular conclusion. Panic is more generic, less specific and a safer choice. In addition, those were very small wrecks, so its not like you could stage it to where she got inside and panicked and got lost and ran out of air. There is not much there to snag on either in order to create a horrendous panic of being stuck on something and unable to escape. That would be like dying of panic with your index fingers stuck in a chinese puzzle. Look at the pictures of those wrecks - do they really look that menacing to you? In addition, she was counting fish - that activity, as Ken pointed out occurs on the reef, not the wreck.
As far as Occam's razor goes, I think we have different views of words like "simple" and "plausible". It's much more simple in my mind for someone to catch their snorkel on a wreck as they poke their head inside to look for fish than to assume a murder.
This really sounds more like an argument for the idea that she didn't actually die. Something killed her and it wasn't a snagged snorkel. A snagged snorkel does not explain a threaded mouthpiece that is ripped off the snorkel. It doesn't explain a missing slate. It doesn't explain a broken mask strap, it doesn't explain a broken mask pin, it doesn't explain a fin that is removed and placed upright in the sand. Jury must have everything explained, not just one little thing.
The whole money thing makes no sense based upon what facts we have here. What happened to all the money? If it went to pay debts he had relating to his shop then it is no surprise that it was spent quickly. Did he buy a shiny new car or put in a hot tub at the house? Buy thousands of dollars in jewelry? I haven't seen any facts relating to where the money ended up.
I don't know the answers, so it's hard to judge. He certainly didn't have much money available to pay the best lawyers to defend him against the civil suit, and had nothing after it was over. The fact that he endedd up broke doesn't prove he wasn't after money, but it doesn't sound like he took any aggressive actions to protect his fortune.
There was a forensic analysis of Swain's financial affairs. He blew through $680K of money that he gained from Shelley's death. The short story is, he blew it on lavish vacations and keeping his dive store operating. However, he was already out of money and bankrupt before the civil trial. Apparently you missed this part and are hoping that the jury will just ignore it - they won't.
You've never heard of anyone killing for money because they wanted to live an extravagant lifestyle and blew through money like it was water without a care in the world? Really?
The problem here is that the defense was put into the position to explain what unusual event occurred under the sea to take Shelley's life. If, as David claims, he wasn't there when she died, then how could he be expected to know what happened to her and to provide a scenario? If he says "I don't know, maybe X happened?", then proving it wasn't X isn't the same as proving he killed her.
This is usually the case for the defense and it really is the nature of how the examination of evidence works. There was a recent criminal defense case I was involved in where all the facts really favored the defense and when it came time to tell the complete narrative story of what really happened, the prosecution had no chance. The evidence must be explained, whether it is the defendant who does it or the defendant's attorneys. David as a witness was in a "I-don't-know-because-I-wasn't-there position." Not a good position for the defendant to be in and I agree with Ken, the defense never should have put him on the stand. The jury really needed to hear him explain the evidence away. He couldn't do it and it hurt him, and did not help him.
I don't know if he did it. I wouldn't be shocked if it were proven either way by some actual evidence. Because of that, and in spite of the persuasive arguments, I would have a hard time convicting him of murder. I can't even imagine doing it with almost no deliberation.
Even though the jury agrees not to formerly deliberate with each other until the case is rested, they are deliberating in their own minds through the entire trial. When they come back in just five hours with a verdict, it means they were all pretty much thinking the same thing. So that tells me that if Swain does get a second trial, he has a real uphill battle to sway the minds of a jury.
