There is no way of knowing of that "strengthened" evidence was the difference between any given person walking or going to jail. They all need to be retried, and imprisoning them until that can happen is an injustice. Give them all the opportunity to make bail again until new trials can be arranged.

If the circumstances of their crime make it such that they cannot be retried (for example, all the substantial evidence was bloodwork that was corrupted and cannot be taken again, many months or years later) then they should be released. Guessing that they actually are bad guys isn't good enough.