Which is worse?
1) Someone being punished for a crime they didn't commit?
2) Someone not being punished for a crime they did commit?
If you can answer the above . . . then you have the answer to "eye for an eye". Societies that adhere to stricter punishments for violent crimes have clearly decided that #2 is the worse outcome. Conversely, societies that believe #1 is the worse outcome have adopted less harsh (revocable) punishments for violent offenders.
This critical thinking can be used to analyse many choices society makes in dealing with broad situations. Here is another example:
Which is the greater wrong?
1) Someone who has the right to vote not being allowed to vote?
2) Someone who doesn't have the right to vote being allowed to vote?
If you can answer this question then you can answer the question of whether you agree or disagree with new legislation that would require a citizen to show official ID to vote.