No, but I think that if I'd sat through the murder trial, being presented with all that evidence in person, I would have also said, "yeah, I'm sure beyond reasonable doubt that she is dead".
Reasonable doubt didn't equal 100% certainty. It was a doubt that was reasonable to have. You can almost always come up with bizarre theories involving identical twins, alien abduction and time travel to exonerate a defendant, but they're not plausible.
To define reasonable doubt further, I think it's best to consider unreasonable doubt first. Imagine that you are going on holiday, and you're in the car to go. You have just checked that you turned the gas off three times, but you still feel an intrusive thought that maybe it is actually still on and you didn't check properly. That's unreasonable doubt. It's never going away, because it has nothing to do with evidence. You will never feel 100% certain that you've really turned the gas off, but you know you have so you grit your teeth and drive for the airport.
Now imagine you are upstairs in bed, and you can't remember if you locked the front door. You lock the front door every night before bed, but you can't remember doing it tonight. You almost certainly did lock it, but there is "reasonable doubt".
In this case, if I had been a juror, the defence's explanation wouldn't have been enough to make me reasonably doubt he did it. I'd consider it was to be an irrational fear. I worry a lot, about everything, especially at 3am, but I don't think I'd ever lie awake, thinking, "but suppose he really was framed by someone and I got it wrong".