The one who takes away from his friend

On Thursday evening, you explained that the rule that excludes a person from the evidence is based on the assumption that what is under a person's control is his, and that this assumption is not a statistical principle (there is a greater chance that the object belongs to the person who has it under their control, because most objects in the world belong to those who have it under their control) but rather an effective legal principle (the chance that it belongs to the defendant is 50%, but there is nothing to be done except for the plaintiff to bring evidence, otherwise everyone in the world will come up with claims against the other).
 
What is the ruling in a city where 90% of the population is thieves? It is also said there that the one who takes away from his fellow? It is also said there that the chance that the object belongs to the defendant is the same as the chance that it belongs to the plaintiff (50%)?
I assume that this was not said, and so we assume that the belonging of the object depends on the probability of what exists in the world, and not what exists in a court of law?