In software technology this is known as data abstraction or information abstraction. The user is just shown the details of what he is required to know and not confused with the internal details.
Well, I am just talking to you in terms of high-level details.
To answer you directly. Firstly you say, you presume. Secondly you say, others believe. How can there be an answer for a little john on the streets' assumptions/presumptions and little beliefs?
Science has answers for most thrilling and rational questions put in a most logical form possible by the human mind. So we call the scientific laws as truths. But do we call the beliefs as truth themselves? No the reason is you and I just believe, we do not question the most rationalistic or logical way to get at the truth of the matter or subject.
Supposedly, let us go by your presumption and others' belief. And every one getting to know of their rewards and punishments. Which means everyone gets to know of who on this planet that is living that they have harmed in a previous life. And me the little John trodding the streets of Bangalore, India knows that another little Peter on a streets of New York, has harmed me. How can I sue him for that which happened in my past life? For that all that little Johns in Bangalore and little Peters in New York should know that there was a past life for them too. And therefore, I am logical and rightly justifying my act of suing and getting him punished. In the absence of such an evidence, that is, only few believe there is a past life and not every one. And only few assume there is a past life and not every one actually knowing it makes it a ridiculous and laughable affair of those few lunatics.
See, what is the status of these believers now. So truth must be known and known by all to be valid at all times. Truth should not be assumed or presumed or simply believed without an experience of all or just only experienced and claimed by a very few. Even only a Jesus claiming that there is a GOD would not satisfy me, only a Muhammed claiming to an Allah would not give me enough proof of a past birth and future punishments.
Far better are high courts, supreme and superior courts for however, much delayed they spell their judgements they do punish a criminal in his own life time.
Do not you know that, "A justice delayed is a justice denied?"
So let you not be unjust to criminals. Be and Do justice to one and all and now and now itself. Hail! justice.