Everything comes down to Law because as soon as a Law is given that allows the option of sin as it is now known what is right and wrong and a choice is given. Without a law there is no right or wrong. Without a law there is no lawbreaker.
So God said do not eat from this tree to Adam and Even, that is a law, they now automatically know eating it is breaking the law and not eating it is lawful. They now have a conscience. That was the very first Law God gave.
If God said eat from this tree if you would like, then you know if you do eat is is ok and not wrong, either way the mind now believes in right and wrong because that's how a law works.
I don't believe Adam and Eve had a conscience until they ate the fruit. They simply knew God said don't eat. God giving them a law, did not create the conscience. They did not yet have the ability to know good and evil.
Quantrill