I'm not sure if this has been mentioned....but as someone who has seizures, they can barely catch them wehn someone is alive, much less dead! My neurologist told me not to even bother going to the ER...it's over and they won't catch it. Many people dx'ed with seizures are never "caught" on machine. I loose consciousness, completely. There are so many types of seizures - some can just be "glitches", some full grand mal, and some people like me who get a rush of heat, sit down and just "go to sleep". Just sayin' (but they can't catch that in autopsy....correct me if I'm wrong)
Anyway, why drain the bathtub? Why move her to the bedroom? Why wouldn't he have just put her on the bathroom floor, and start working on her there?
So many questions...but I agree, there's reasonable doubt.
ETA: It would be really "funny" that her first huge seizure would be in a bathtub. Usually there is a trigger (not always). I.e. - usually two days after a very stressful event, i'll usually have one. I compensate by taking more seizure meds and maybe a benzo to try and prevent. I also don't go sit in a bathtub or go around strobe lights, etc.