Its the one thing I never understood about a jury based justice system and that is that the jurys are not overseen by any kind of offical to make sure they are complying with the law. Its a trust based system that leads to stuff like this.

Not talking about someone who interacts with the Jury but someone impartial who stays in the room offers no imput but can report any violations of the law or a judges order back to the court for example if they where told not to discuss certain evidence and they start doing.

Simply a witness that the jurys deliberation happened within the law and as ordered.