I think panic is really a distraction. If the prosecutor can't show Watson turned off Tina's air or removed her reg, the case is pretty much over. If the prosecutor can't show Watson turned off Tina's air or removed her reg, then it is unlikely the prosecutor could show that abandoning her directly led to her death, i.e. that she would have lived but for having been abandoned.
Panic is relevant only to explain Watson's apparently bizarre behavior and seemingly inconsistent statements and to negate those as evidence of intent to kill.
Sorry - but Watson basically already pled guilty and served time for abandoning his wife and letting her die. I don't see how you can come to this conclusion. Here is an excerpt from the Australian prosecutor's sentencing appeal:
"..He virtually extinguished any chance of survival by allowing her to sink to the sea bed. This case is therefore quite different from those cases where there is a small risk which an offender had not appreciated or hoped would not eventuate
at no point did the offender change his mind and go back to Mrs Watson and attempt to bring her back to the surface. His breach of duty was not merely a momentary one
it is almost inexplicable that he made the decision to leave her...
"..the respondent undertook, in potentially serious circumstances, to shield from harm an inexperienced diver, whose inexperience had been declared before him, on the basis he would undertake a duty which a professional would otherwise discharge; the one thing he was called upon to do, to bring Mrs Watson to the surface, was simple to accomplish, and his failure to carry it out is unexplained; and there is no circumstance disclosed, eg panic, which would have explained it.."
Source:
Tina Watson Dies While Scuba Diving with Her Husband - Sentencing Appeal - Sep 18, 2009 - Part 1
In addition, there were questions of this being criminally negligent homicide. That was the finding in the Australia case. Here is a section from the prosecutor's appeal:
..One must be careful in assessing the applicants crime not to excuse the result as accidental, because obviously to do that would be inconsistent with the verdict. He is to be sentenced for a criminally negligent killing, not an accident..
..A criminally negligent killing of a human being should, in general, warrant a substantial period of imprisonment. A head sentence of four and a half years does not adequately reflect the communitys justified revulsion at conduct admitted to be criminally culpable and by which the respondent killed a young woman.
This is what Watson pleaded guilty to and spent 18 months in prision for. I don't think he can pretend in Alabama that this was not the case.
Other previously asked questions are also contained in this sentencing appeal, which was submitted by the Australian prosecutor:
Christina clearly trusted the offender as husband and buddy. He had much greater diving experience than her. The respondent took on the responsibility of being her buddy on this dive despite the recommendation that she undertake an orientation dive with a dive master. It was the respondents level of experience that led the dive operators to allow her to participate in the dive with the respondent.