Affirmative Defense

Affirmative defense is a legal term that pertains to a defendant’s response to being accused of a certain crime. When an affirmative defense is used, the defendant is basically admitting he committed the crime of which he is accused, but is offering an explanation or justification for the incident. When successful, an affirmative defense can help reduce the defendant’s legal liability. To explore this concept, consider the affirmative defense definition.

Definition of Affirmative Defense


  1. A defense used in a criminal or civil case which, if determined to be credible, can exonerate the defendant, or reduce the defendant’s culpability.

What is Affirmative Defense

An affirmative defense is used in response to a civil lawsuit or criminal charges, when the defendant admits guilt or wrongdoing, but introduces facts or explanations to justify his conduct. A defendant can also use an affirmative defense by responding to allegations against him by bringing his own charges or evidence not presented in the plaintiff’s complaint.

The laws regarding affirmative defenses vary by jurisdiction, but they must be made in a timely manner or the court mays refuse to consider them. There is one affirmative defense that cannot be waived or refused. It is lack of subject matter jurisdiction, which means that the court in which the action has been brought does not have the authority to hear it, or to render a decision.

For example:

Samuel has been charged with domestic violence. During a hearing in criminal court, his wife asks the court to give her sole custody of the couple’s daughter. The criminal court does not have subject matter jurisdiction, meaning it does not have the authority to hear matters of child custody. Even if Samuel is found guilty of the crime, his wife will need to go to family court to have the custody matter decided.

Types of Affirmative Defense

In criminal cases, an affirmative defense is a legal excuse for committing a crime. In order for someone to be found guilty of a crime, he must have performed an act that is against the law, and generally must have done so with the intent of wrongdoing, or with a mental state that gives rise to criminal liability.

There are a number of situations in which society simply does not condone punishing a person for technically committing a crime. When an accused person admits to having committed a criminal act, but provides a reason for the act that is generally accepted as being an exception to punishment, he is offering an affirmative defense.

There are several nationally recognized affirmative defenses, but the most common being self-defense, necessity, entrapment, and insanity.

Self-Defense or Defense of Others

Defendants charged with serious crimes, such as murder or assault, may use self-defense, or defense of another person, as an affirmative defense. In such a case, the defendant admits to committing the crime against another person, but presents evidence to the court showing that the alleged victim posed a danger to the defendant’s life or well-being, or to that of another person. For self-defense to be a successful defense, certain elements are necessary:

  • The defendant had a reasonable belief there was a threat to his life (or the life of someone else)
  • There was not a reasonable alternative to the defendant’s actions
  • The force used was not greater than necessary to end the threat posed by the alleged victim

Example 1:

Jane has been charged with first-degree murder for the death of her husband. To prove the charges, the prosecution must present the court with evidence that the crime was premeditated. In simple terms, the prosecutor must show the court that Jane planned the murder before carrying out the act. The prosecutor has DNA evidence connecting Jane to the murder, but has no convincing evidence that she planned the murder ahead of time.

The defense team uses self-defense as an affirmative defense. They present the court with photographs and testimony from doctors showing that Jane had been badly beaten the night she killed her husband. This affirmative defense is used to justify Jane’s behavior, which could exonerate her completely, or may encourage the court find her guilty of a lesser charge, or limit her punishment.

Example 2:

Ruth hears screaming outside her home, and runs outside to find a teenage boy beating her son with a baseball bat. In fear for her son’s life, Ruth grabs a shovel and hits the boy in the head, knocking him unconscious. The boy later dies from the head injury, and Ruth is charged with Second Degree murder.

Ruth’s defense attorney uses defense of another as an affirmative defense, claiming that Ruth did what any reasonable person would do when in fear for another’s life. Depending on other facts surrounding the case, such as testimony of the assaulting boy’s criminal history, or history as a bully, and witness accounts, such an affirmative defense may exonerate Ruth completely.


When necessity is used as an affirmative defense, the defendant argues that he engaged in the illegal conduct with the purpose of doing whatever was needed to prevent a greater harm. In order to be successful with the defense, the defendant must show the court that:

  • The harm avoided posed a greater danger than the prohibited conduct
  • There was no reasonable alternative to the prohibited conduct that would avoid the greater danger
  • The prohibited conduct stopped as soon as the danger was gone
  • The defendant was not responsible for the danger that needed to be avoided

For example:

Sherry is pregnant and in labor. When her water breaks in the car on the way to the hospital, her husband drives much faster, afraid the baby would be born before he could get to medical care. Though Sherry’s husband broke traffic laws, necessity can be used as an affirmative defense, as he could see no reasonable alternative to getting his wife to the medical center.


Entrapment is an affirmative defense that may be used when a defendant admits to having committed a crime, but claims he did so because a law enforcement official, or other agent of the government, enticed him to do it. In order for this defense to be successful, the defendant must show that he would not have committed the crime without the agent’s participation or influence.

For example:

Josh is charged with selling his prescription medication to an undercover officer. The undercover officer appeared at Josh’s home begging for the drugs, claiming her mom was sick and would die without them. Josh repeatedly refused, but eventually sold her some of the drugs. Josh was arrested, but eventually found not guilty. The jury determined that the agent’s repeated harassment and lies constituted entrapment, and that it was unlikely that Josh would have sold his medications otherwise.


The insanity defense may be employed if the defendant admits to having committed the crime, but was incapable of understanding his actions, or of knowing right from wrong, at the time of the crime, due to diminished mental capacity. Proffering an insanity defense is a very complex issue, requiring the evaluation by, and intervention of, a variety of professionals. A verdict of not guilty by reason of insanity, or of guilty but insane, does not usually mean the defendant will simply walk free. It is possible he or she will spend more time in a mental facility than he would have in prison, had he simply been found guilty.

For example:

Bradley suffers from schizophrenia. During an episode, he believes that his neighbor Marty is trying to kill him. Bradley pushes Marty down the stairs in the apartment complex, breaking Marty’s leg. Rather than being sentenced to prison for aggravated battery, Bradley is convicted of a lesser charge, which sentence includes confinement to a mental institution.


In rare cases, being intoxicated by alcohol or drugs during the commission of a crime may be used as an affirmative defense. If the defendant was intoxicated due to his own actions, having willingly drank excessively, or used drugs, an intoxication defense is not usually accepted. This is because the defendant had diminished his own mental capacity, and is therefore liable for his actions while under the influence. If, on the other hand, the defendant had been given drugs against his will, then committed a crime as a result of his forced intoxicated state, an affirmative defense of intoxication may be effective.

Affirmative Defenses in Civil Lawsuits

Affirmative defenses are also used in civil lawsuits, when the defendant admits that the events did occur, but claims there is a valid explanation for what happened. In civil cases, affirmative defenses are used to free the defendant from all responsibility, or to reduce the amount of his liability. Some common affirmative defenses used in civil cases include:

Comparative Negligence

In a comparative negligence affirmative defense, a defendant claims that the plaintiff is at least partially responsible for the harm caused. If the defendant is successful in this defense, the court is likely to distribute liability between the parties according to their comparative percentage of liability.

For example:

While driving after dusk, in the rain, Annie makes a left-hand turn, and crashes nearly head-on with another car. While the other driver blames Annie for the accident, Annie asserts an affirmative defense of comparative negligence, testifying that the other driver had no headlights on. If there is evidence to show that is true, the court is likely to assign a percentage of fault to each driver, and the damages will be split accordingly.

For instance, Annie’s damages amount to $4,000, and the other driver’s damages amount to $6,000, for a total of $10,000. The judge splits liability evenly between the drivers, at $5,000 each. Alternatively, the court may order each party to absorb their own damages, with no award to either driver.

Limited or No Harm

When using a limited harm, or no harm, affirmative defense, the defendant claims that the plaintiff suffered no harm, or that his damages are very small, or less than he claims. If there are no damages, no physical harm, no financial harm, or no harm to some other aspect of the plaintiff’s life or health, there is no case.

For example:

Max drives into the rear of Neal’s car at a stop sign. It appears the cars high bumpers, and there was no visible damage to either car. The two exchange insurance information and leave the scene. A few weeks later, Neal files a civil lawsuit against Max, claiming damages to his vehicle, and an injury to his back.

During the trial, it becomes apparent that Neal did not go to the hospital or to his doctor after the accident, even though he is claiming to have pain every day, and asking for $10,000 for pain and suffering. There is no proof that Neal suffered any injury at all, and photos taken at the time of the accident show no damage to the cars. An affirmative defense of no harm in such a case is likely to be successful, with a ruling against the plaintiff.

Intervening Cause

An affirmative defense of intervening cause may be used if the defendant shows the court that, while the plaintiff suffered injuries or damages due to the defendant’s negligence, those injuries or damages were made worse by the plaintiff’s actions following that incident.

For example:

Maria trips over an unkempt section of floor at the grocery market, causing her to sprain her ankle. Without going to the doctor to have her injured ankle examined, Maria goes skiing a few days later, where she falls and breaks that ankle.

If Maria sues the grocery market for her injury, it is likely the store would bring an affirmative defense of intervening cause, claiming that it was the skiing accident that cause Maria’s injuries, not her fall at the store. With no medical records to say differently, there is a good chance this defense would be effective.

Affirmative Defense vs. Negating Defense

An affirmative defense is used to justify, or provide an explanation for, the defendant’s illegal conduct. Conversely, a negating defense involves attacking one or more elements of the prosecutor’s or plaintiff’s case. Because the prosecutor or plaintiff has the burden of proving his case, a defendant can use a negating defense to bring doubt about one or more essential elements of proving the case.

A negating defense is more likely to be successful in a criminal case, as the prosecution must prove each element of the crime beyond a reasonable doubt. Therefore, creating doubt about the crime, through physical evidence, video evidence, eyewitness testimony, or other evidence, may result in acquittal. An affirmative defense, whether in a civil or criminal matter, may be more difficult to accomplish, as it requires showing the court there is some good reason or justification for committing the crime, or causing the damages.

Example of Negating Defense:

Jeremy has been charged with theft of property valued over $500, which is a felony. At trial, Jeremy’s attorney provides evidence that the property in question has a value of only $249. This fact negates the charge entirely, as Jeremy has not been charged with petty theft, or theft of an item valued under $500.

Mother Claims Insanity as an Affirmative Defense

On January 14, 2010, a 3-year old little girl drowned in her bathtub. When emergency personnel arrived at the home, they found the girl still in the bathtub, and the mother, Jennifer, with a number of superficial, self-inflicted knife wounds to her chest. After being treated at the hospital, the mother was taken into custody, and charged with suspicion of murder of her little girl.

Jennifer’s attorney used the affirmative defense that the mother was not guilty by reason of insanity. The court ordered an immediate psychiatric evaluation, and she was treated at a local hospital. During trial, two doctors testified that, while it was apparent Jennifer had suffered a psychotic break at the time of her daughter’s death, she no longer exhibited symptoms of mental illness. Jennifer was found not guilty by reason of insanity, and was sentenced to three years of treatment while incarcerated.

Related Legal Terms and Issues

  • Acquittal – To be relieved from a criminal charge; to be declared not guilty.

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