No, that's not what he said. What he said was that, after 15 years, there was no way to determine whether or not that was the cause.
The M.E. said he is still open to new evidence on that matter. Is that not correct?
The low potassium reading was not the only blood abnormality of interest. Terri was acidotic. Lactic acidosis usually involves a lot of exertion (or bad circulation in elderly patients). How this could have occurred if she just got up to go to the bathroom is, to say the least, unexplained.
Cardiac arrest was due to anoxia. What caused the anoxic episode has been the whole question all along. Lactic acidosis is consistent with Terri struggling frantically to breathe with her oxygen cut off. The fact that anoxic damage occurred in her brain but not in her heart, liver or kidneys is also suggestive of where the oxygen was cut off.