After numerous scientific studies, we have determined that free will does not exist. Is this correct
Not necessarily, as it's kind of hard/impossible to say something like free will does or doesn't exist.
It could just be that free will does exist, but choices just always happen to line up with environment.
What we do know is that people raised a certain way tend to become a certain person. People with certain genes tend to act certain ways. People with a modified mind make different decisions. We can predict what a person is about to do based on the state of their mind.
All evidence for the idea that our "choices" are not something determined, but something you could predict accurately if you knew everything about the world at time N, and had the right math/simulation ability to predict N+1.
No time would that prediction be wrong, no time would the person make a choice that would go against that prediction. We are literally the matter, the reactions, that make us up, and our decisions are also a result of that.
"Now we can judge a criminal for his actions based on his own decisions"?
We can still do that.
A person is who they are born as. They don't choose to be that person. A person is what the world around them makes them. This doesn't make them excluded from their choices, in fact, it makes them all the more tied to them. That person, the things that person did, are inherently who that person is.
Rather than a "disconnected" being making decisions, a criminal is a person who makes the decision to kill, to steal, and so on. They don't make the decision to become that, but they are still that, and we should still treat them as such. Just as we should remember that we can change that path, change their environment, to turn them into someone different, someone productive for society. AKA: Jail.
How would the universe need to be different to be one where free will would exist?
If free will were a thing, we wouldn't see decisions tied to the environment, the birth, and so on. They would be "free" of physical factors, unable to be predicted. Two equally likely outcomes, and the person picks which comes true.
To my knowledge, that reality does not exist.