> The entire legal system is supposed to be based on the concept that it is better to let the guilty walk than destroy an innocent person.

This is true if you believe that there is a final justice. However, in a secularizing society that doesn’t believe in God or final judgement, if you want justice it has to be here and now since it will not come any other way.

How can you call that justice when innocents are imprisoned for crimes that did not commit while the criminals go free ?

That concept comes from the belief that it is worse to punish an innocent than to let a culpable go free. Call that utilitarian if you will but it has nothing to do with a hypothetical final judgment.

On the contrary, how can you rationalize locking up an innocent person unless you believe they will be redeemed at The End?

True. Too many people accept the evil of false convictions because they believe in life eternal, that unjust suffering during life will be rewarded afterwards. I'd rather get things right now than roll those dice.

I get the logic here. But in many religions god is the source of justice. Got no idea if OP is a Christian or not but there are plenty of judicial proceedings in portions of the Bible that lots of Christians overlook, particularly about the requirement for at the least two or three witnesses (which doesn't necessitate eyewitness but at least two credible witnesses) before a conviction takes place. There is also plenty of case law in the Hebrew scriptures about not imprisoning or punishing someone if there is no evidence (e.g. establishment of sanctuary cities for accused persons to go to while a just trial is pending).

Just to pick a small nit here, OT law is not considered binding on Christians today by most Christian theologies.

It's valuable for understanding the NT, but not considered binding as law.