A hand print on the bible proves what? I also think you're wrong and it is Sheila's.
It would prove there was blood on her hands, It is very significant because the Jury were told her hands were clean. It also heavily damages the pathologists credibility as a whole who told them they were clean.
It will also prove her bloody hand made contact with PSAMS 51-55 This is even more significant because they contain the passages.
"Have mercy upon me, O God"
"Deliver me from bloodguiltiness O God, thou God of my salvation"
"My heart is sore pained within me: and the terrors of death are fallen upon me"
It can also be demonstrated that Sheila placed her hand there while she was alive.