The jury must consider what logical and obvious inferences can be drawn from the evidence.
If more than one inference can be drawn, and one doesn't support guilt - then a not guilty verdict has to follow.
For example, I find suicide to be speculative. There is no real evidential foundation to infer she committed suicide IMO
Libby blundering into the river by accident, i would normally find to be a bit too coincidental and convenient, unless the evidence is showing it more or reasonably likely it happened that way (
@Tortoise 'analaysis)
When the evidence leads in one direction, then events that are normally rare, become more probable