By the time of Jesus the principle was being misapplied. Men were using it is justify their desire for personal revenge and neglecting the matter of mercy. Ever seeking justice for themselves they failed to realise that what they most needed was forgiveness. If they wanted mercy from God they needed to offer mercy to men.
In our own age that has had 2000 years of Christendom teaching mercy we risk neglecting justice for others. It is true that we need to allow vengeance at God's hand and not pursue personal vendettas, even so, victims require justice, and God has given us his principles for justice.
At its most simple the principle of talion is to require the criminal to receive what he has done. This is restricted to permanent personal damage done intentionally, or at least caused by gross criminal negligence. Thus,
- Remove an eye: lose an eye
- Kill a person: be executed
There are several aspects to the talion. The first is that punishment is limited. Limited to the level at which a crime is performed. If a man is intentionally causing permanent injury to another then the consequence for him can be no greater than the harm caused. If he blinds a man in one eye you cannot blind him in both. If he cuts off a finger you can't cut off an arm. Related to this is the fact that, excepting execution, one cannot be maimed for infractions that do not maim others. A thief is not to have his hand cut off. A voyeur is not to have his eye plucked out.
Certain crimes are still capital offences. Treason, adultery, etc may still require the death penalty but judges are not permitted to maim and mutilate indiscriminately.
A second aspect is that men are to be punished if they give fraudulent evidence that may cause maiming. When a man falsely testifies to something that would lead to damage he is to receive the same,
If a malicious witness arises to accuse a person of wrongdoing, then both parties to the dispute shall appear before the Lord, before the priests and the judges who are in office in those days. The judges shall inquire diligently, and if the witness is a false witness and has accused his brother falsely, then you shall do to him as he had meant to do to his brother. So you shall purge the evil from your midst. And the rest shall hear and fear, and shall never again commit any such evil among you. Your eye shall not pity. It shall be life for life, eye for eye, tooth for tooth, hand for hand, foot for foot. (Deu 19:16-21)The command that your eye shall not pity may mean that the judge is not permitted to give a lesser punishment or substitute a fine; it is a minimum sentence.
The implications of this principle are striking. Essentially a false accusation incurs the guilt of the crime. A man accusing someone of murder bears the guilt of murder. A woman who falsely claims rape is as guilty as a rapist.
 The only exception appears to be if a woman grabs a man by his testicles during a fight. In this case she was to have her hand cut off and a fine could not be substituted (Deu 25:11-12). One possible explanation is that such behaviour could cause injury to the testicles (such as sterility, the context concerns descendants) so she was to receive a punishment that was appropriate. This would be her hand as females do not have testicles and she used her hand to commit the offence.