I think the case was fairly straightforward if you take out all of the hand waving, sidebars, shenanigans and flotsam.
- Jurors first have to determine if Kathleen's death was an accident or not. Two or three highly regarded pathologists looked at the case, the autopsy, the pics, the scene, and determined the injuries KS sustained were not caused by (just) a fall in the tub and the injuries could not have been made by only one fall.
- Kathleen had no illegal drugs or alcohol in her blood. There was no medical reason determined for her to fall and land the way she did.
- The scene does not look like an accident (placement in the tub, lack of water, etc).
- The scene appears to have been altered (blue towel / no blue towel)
- Statements from Stacey Peterson that DP killed Kathleen, he was gone that night, had women's clothes, washer, etc., corroborated by a few people.
- DP's own statements at various times to various people.
It's actually pretty clear the pieces are there to convict. It doesn't mean a jury WILL convict, but they have enough to take them over the line of reasonable doubt to convict if they can work through it.