Jurors aren't "allowed" to consider all manner of things but being stupid humans, they frequently do. Like in the Casey Anthony trial (I'm operating from memory here), after the acquittal one of them said in an interview, "They didn't show us a motive." Motive should never have been a matter for them to consider in a murder trial. It's not required in the standard of proof at all. It's something people learned from cop and lawyer shows on TV. You can tell jurors they're not "allowed" to consider things right and left, you can tell them to disregard things they heard that turned out not to be admissible, but they're going to do their own thing once they're in that room.