Self-defense is a defense commonly asserted by someone charged with a crime of violence (murder, battery, etc.). If a defendant claims he acted in self-defense, he admits that he did in fact commit the crime but claims his actions were justified by the victim's threatening actions. In evaluating whether you might be able to successfully argue self-defense for your client, you should determine whether there is evidence of a physical struggle (e.g., whether your client has scratches or other injuries) and also pay attention to the relative size of your client and the victim.
Self-defense and related defenses are based on the theory that people should be allowed to protect themselves from physical violence. This means that a person does not have to wait until he is actually hurt by another to use self-defense. In a majority of United States jurisdictions, there is no duty to retreat (remove oneself from the situation) before acting in self-defense. That means that a person can use deadly force in self-defense even if this could be avoided by retreating.
In the United States, there are different elements self-defense based on the circumstances and type of force used.
Non-Deadly Force - If the defendant uses non-deadly force, generally all the defendant has to show to escape conviction is that the force was reasonably necessary to protect himself from the imminent use of unlawful force and that he was without fault.
Deadly Force - A person may use deadly force in self defense if each of the following elements is met:
- He is without fault. A person who has initiated an assault or provoked the other party will be considered the aggressor and will not be eligible for self-defense except in certain circumstances described below;
- He is confronted with unlawful force. The attacker must be using force that is a crime;
- He is threatened with imminent death or great bodily harm. The defendant must reasonably believe that he is faced with imminent death or great bodily harm if he does not respond with deadly force. The danger of harm must be imminent. There is no right to use deadly force if harm is simply threatened at a future time or the attacker has no present ability to carry out the threat. For example, if a person threatens to kill someone while his hands are tied behind his back, the person threatened will not be justified in using self-defense.
Right of Aggressor to Use Self-Defense - Generally, the person who starts a fight has no right to use force in his own defense during that fight. However, an aggressor can regain his right to use self-defense in two circumstances:
- Withdrawal. Withdrawal occurs if in good faith the aggressor removes himself from the fight and communicates to the other person his desire to remove himself. If the other participant in the fight rejects the withdrawal or continues to fight, the initial aggressor can use force in self-defense.
- Sudden Escalation. If the victim suddenly escalates a minor fight into one involving deadly force without giving the aggressor a chance to withdraw, the aggressor can use force in self-defense.
In India, a 2010 Supreme Court decision  announced its approach to the law of self defense, with ten separate elements:
- 1. Self-preservation is the basic human instinct and is duly recognized by the criminal jurisprudence of all civilized countries. All free, democratic and civilized countries recognize the right of private defence within certain reasonable limits.
- 2. The right of private defence is available only to one who is suddenly confronted with the necessity of averting an impending danger and not of self-creation.
- 3. A mere reasonable apprehension is enough to put the right of self defence into operation. In other words, it is not necessary that there should be an actual commission of the offence in order to give rise to the right of private defence. It is enough if the accused apprehended that such an offence is contemplated and it is likely to be committed if the right of private defence is not exercised.
- 4. The right of private defence commences as soon as a reasonable apprehension arises and it is co-terminus with the duration of such apprehension.
- 5. It is unrealistic to expect a person under assault to modulate his defence step by step with any arithmetical exactitude.
- 6. In private defence the force used by the accused ought not to be wholly disproportionate or much greater than necessary for protection of the person or property.
- 7. It is well settled that even if the accused does not plead self-defence, it is open to consider such a plea if the same arises from the material on record.
- 8. The accused need not prove the existence of the right of private defence beyond reasonable doubt.
- 9. The Indian Penal Code confers the right of private defence only when that unlawful or wrongful act is an offence.
- 10. A person who is in imminent and reasonable danger of losing his life or limb may in exercise of self defence inflict any harm even extending to death on his assailant either when the assault is attempted or directly threatened.