The court can't read the mind of the accused. So either there is an implied level of guilt associated with mere possession or it would be impossible to ever get

The court can't read the mind of the accused. So either there is an implied level of guilt associated with mere possession or it would be impossible to ever get a conviction under that part of the law. I now agree that the "they planted it" defence would work but in practice that would be impossible to prove, which was probably what happened here.