re: What percentage doubt would cause you to acquit?

If a sound argument is presented, and there are no logical fallacies involved, I would be likely to believe reasonable doubt exists.

I'm not talking Richard Kimble, one-armed man stuff. I'm saying, if there are procedural issues; if logical leads are not investigated; if there is a problem with motive or opportunity -- then I could see myself having doubts.

The first two things I would look at would be the classics: motive & opportunity. Would have to establish both soundly, backed with compelling evidence.

If I had an inkling that shoddy police work took place, then I would have serious reservations. After all, it's their job to collect, handle, and catalogue evidence properly. If they don't, that's a big ding. This is their job, and if officers can't do it effectively, they have no business wearing a badge. And the onus is not on the jurors to connect the dots. You can't blame them because someone in law enforcement drops the ball. Wouldn't feel guilty about it, either. If the DA or investigation unit doesn't do their jobs effectively, and I get any sense of mishandling or ineptitude, then I would probably start to have reservations about voting guilty.