DrWatson, unfortunately or fortunately, it wasn't my "opinion" but a peer reviewed information. I was not referring to any particular method of injection. For some reason, you decided that it had to be intravenously because this is how they do it in the movies. However my concern was only about the end result. I am concerned that it may turn out that the COD is officially undetermined, therefore, there is no murder. The available evidence somewhat points that GBC wished to kill his wife and may be knows more about her death, but that's it.
Back to air embolus. In 35% cases cardiac arrest is not related to heart problems. It is a quite common COD, statistically, thus not usually treated as suspicious. The most common non-cardiac causes: trauma, non-trauma related bleeding (gastrointestinal bleeding, aortic rupture, intracranial hemorrhage), overdose, drowning and pulmonary embolism. If we put pulmonary (which is only 15% of all CAs) embolism aside (although with GBC's army training you never know), we still have trauma and/or drowning as a possibility.
About arterial air. Well, yes, no arguments about that, it often goes peripheral but often enough it produces ischemia of any organ with poor collateral circulation. Often enough arterial air causes fatal cardiac arrhythmias (VT -> VF). As a murder method it seems a bit too sophisticated for GBC and a bit too lengthy timewise, in my opinion, but as a possibility - why not?
I have also been thinking of the trauma triad of death as a method. Again, it would have been too sophisticated for Bruce Overland to even comprehend, but if the COD is undetermined, what else to think?