Criminal acts require the accused to willingly violate the penal code without defense. Defenses are legal pretexts found in statutory and common law that mitigate a defendant’s guilt if true. Most defenses fall under one of two categories: excuses and justifications. Defendants who violate criminal law, but claim their free will was compromised proffer excuses. Justifications, as the name implies, are criminal acts that are warranted based on the circumstances of the incident.

Types of Justifications
Self-defense, necessity, duty and consent are justifications frequently used in criminal proceedings.

If a defendant proves that the act she is accused of was necessary for her own survival, she may be exonerated through the justification of self-defense. There are several elements associated with this defense that must be demonstrated as true, however. First, the defendant must show that there was clear and present danger that would have resulted in her losing her life or suffering severe bodily harm if she did not defend herself. Secondly, there must be proof that the defendant was unable to escape before defending herself. Finally, the amount of force used on an assailant must be comparable to the threat posed (e.g., deadly force is not authorized if the defendant was merely shoved). The justification of self-defense may extend to the protection of others if the defendant reasonably believed no other alternative was available.

A criminal lawyer may present the justification of necessity on behalf of his client if greater harm would have occurred if the law wasn’t violated. The most notable and extreme example of this defense is the case of The Queen v. Dudley and Stephans where two men stranded on a boat ate a sick companion to prevent starvation. Other common examples of necessity include trespassing on private property to help someone, violating the speed limit to get an injured person to the hospital and damaging property in an effort to put out a fire. Duty is similar to consent, but typically reserved for individuals operating in an official government capacity like police officers and members of the military. This defense is used in criminal law to justify instances where officers shoot civilians or firemen damage property when combating fires.

Consent is often used when someone is injured or killed after prior agreement amongst all parties to participate in the act resulting in such harm. Mutually agreed on fistfights and injuries sustained during sporting events are the most likely scenarios where a criminal lawyer will rely on such a defense. Providers of medical service may also claim consent if the resulting care was agreed to by the patient and the harm caused was not due to negligence.

Types of Excuses
Insanity, entrapment and duress are excuses habitually used in criminal law to exonerate a defendant. If a defendant demonstrates that he was suffering from a mental disease or emotional instability that inhibited his ability to understand the nature of his criminal act at the time, insanity may be used to avoid a guilty plea. This defense exists due to the belief that criminal perpetrators should only be punished for crimes they purposely commit. Use of this defense may not mean a criminal is free, however. Individuals deemed mentally insane may be sentenced to mental institutions.

If government agents or local law enforcement officials trick a defendant into breaking the law, the defense of entrapment may be used. This defense exists to limit the scope of law enforcement and protect the civil rights of citizens. Duress is founded on a similar principle. Defendants claiming duress must prove that they violated the law due to threat of harm to them or someone close to them, blackmail or extortion.