First Degree Murder Defenses

We've all heard the expression that someone "got away with murder." It often comes up when a person seems to avoid punishment for misconduct. Similarly, during an infamous criminal case, people may wonder if the defense attorney will get the defendant "off." In other words, can they beat the case?

When a criminal defense lawyer signs up or gets an appointment to defend someone charged with first-degree murder, they must make the state prove its case beyond a reasonable doubt. The outcome of the case will affect a person's life and liberty. Their defense may lead to a "not guilty" finding that allows their client to walk free. Often, it may result in consideration of other circumstances that bring about a just result. This includes a conviction for a lesser offense.

This article discusses legal defenses that arise in first-degree murder cases. Some of these possible defenses focus on deficiencies in evidence and could lead to an acquittal. Others may mitigate sentencing or lead to a reduction of charges to second-degree murder or manslaughter.

What Is First Degree Murder?

Federal and state laws all contain the crime of first-degree murder. It represents the most serious crime in the law. Punishment can include:

  • A life imprisonment sentence with the possibility of parole
  • A life imprisonment sentence with no chance of parole
  • The death penalty

Federal law defines murder as the unlawful killing of another person with malice aforethought. It identifies first-degree murder (18 U.S.C. Section 1111) as murder perpetrated in any of the following ways:

  • Poison
  • Lying in wait
  • Any other kind of willful, deliberate, malicious, and premeditated killing
  • A killing that occurs in the perpetration of (or in the attempted perpetration of) arson escape, murder, kidnapping, treason, espionage, sabotage, aggravated sexual abuse or sexual abuse, child abuse, burglary, or robbery, or part of a pattern or practice of assault or torture of a child or children. (A killing during certain felonies is also known as felony murder.)

State laws vary in how they define and what they call their highest charge of murder. Not all states include felony murder offenses in their first-degree murder statute. Many states also name specific circumstances that elevate a murder to the first degree.

For example, Pennsylvania law says first-degree murder happens when a person intentionally causes the death of another human being by any of the following:

  • Poison
  • Lying in wait
  • Any other kind of killing that is willful, deliberate, and involves premeditation

Yet, that state also has a separate statute for criminal homicide in the first degree where the offender kills a law enforcement officer. This offense requires that the officer was performing their duties at the time. The offender must also know that the victim is a law enforcement officer.

First-Degree Murder Defenses: Mistaken Identity

In first-degree murder cases and other homicide crimes, defendants often claim the defense of mistaken identity. That is, they claim the prosecution has charged the wrong person with the killing. The defendant may say they have an alibi. They may show evidence supporting their claim that they were elsewhere during the killing.

A mistaken identity defense can include challenges to the evidence that places the defendant at the crime scene. They may question witness identification or contest forensic evidence. The defense attorney may try to suppress evidence of a suggestive lineup or photo array.

A mistaken identity defense may also point to evidence implicating another suspect. Still, the defendant does not have an obligation to do that.

First-Degree Murder Defenses: Failure to Prove the Elements

First-degree murder is a crime with specific elements, each of which the state must prove beyond a reasonable doubt. The defense attorney will review the elements of the crime in the state law at issue. If one of these elements is missing, the accused should not face charges of first-degree murder. For example, if there is little or no evidence of premeditation, there may be good cause for a lesser charge, such as second-degree murder or manslaughter.

While the defense may raise doubts about the state's evidence on one or more elements, it doesn't have to do so. To convict the defendant, the prosecutor always carries the burden of proving each crime element to the jury.

First-Degree Murder Defenses: Justification

The defendant may admit to killing another person but claim there was justification for the offense. Justification provides a complete defense to charges of first-degree murder. Some of the most common justifications are self-defense, defense of others, and exercise of duty. Other justification theories are more challenging to prove and aren't used often in homicide cases. These include the defense of necessity or choice of evils.


Causing the death of another person in self-defense is the most common justification defense. To succeed, a defendant must show that they had a reasonable fear of death or serious physical harm that led to the killing. Words or insults would not suffice.

The defendant can't have started the fight or instigated the threatening situation. The degree of force must be proportional to the perceived threat. The defendant's reaction to the threat can't take place after the threat of death or serious physical harm has passed.

Many states require that the defendant try to retreat or avoid danger, if possible, before resorting to the use of deadly force. These states don't allow claims of self-defense when the defendant could retreat to safety. States differ in how they define such a retreat. No state requires a retreat from a deadly threat inside one's home.

According to the National Conference of State Legislatures (NCSL), more than half of states now have "stand your ground" laws. These laws impose no duty to retreat. Some criminal justice experts say this could cause violent confrontations to escalate.

In Florida, the "stand your ground" law is well known for its use in the George Zimmerman case. Zimmerman killed 17-year-old Trayvon Martin, an unarmed black teenager walking home at night. Zimmerman claimed that Martin started a physical confrontation with him. He claimed he shot and killed Martin in self-defense. Under Florida's version of the "stand your ground" law, the state had to prove beyond a reasonable doubt that Zimmerman was not acting in self-defense. Ultimately, the jury acquitted him of second-degree murder charges.

Defense of Others

In some cases, a defendant may claim they acted in defense of others as justification for killing another person. If you believe you should intervene, you can defend another from harm. The person you help must have a legitimate self-defense claim. The use of force must be timely and proportional to the threat faced. The perceived threat of death or bodily harm must be reasonable. If a threatened person could use deadly force to protect themselves, you could use that same force to end the threat.

Exercise of Duty

Certain killings by law enforcement and other public officers qualify as justified homicides. An on-duty officer has the authority to use appropriate force to defend others and to stop a crime in progress or a fleeing felon. If an officer acts consistently with their authority, the law may justify them in killing another person. Such a homicide would not constitute murder, let alone first-degree murder.

Some states, like California, have penal code provisions that protect police officers and other officials acting under their command. These laws may provide sanction for an officer-involved killing as long as the officer did not use excessive force.

Prevention of a Crime

Some state laws allow those not in law enforcement to use force to prevent certain dangerous types of felony crimes. This may include robbery, kidnapping, arson, and burglary. Texas allows noteworthy leniency. Its statute authorizes using deadly force to prevent misdemeanor theft at night.

Battered Woman Syndrome

The concept now known as battered woman syndrome gained acceptance after its description by Lenore Walker in 1979. The term refers to a pattern of psychological and behavioral symptoms in women in abusive relationships. These relationships may involve patterns of domestic violence (also called intimate partner violence).

Most often, battered woman syndrome appears with self-defense claims. For example, an Ohio statute says the syndrome may be the subject of expert testimony in any case involving the use of force against another. The expert testimony could help a judge or jury decide if the defendant had "the requisite belief of imminent danger of death or great bodily harm" to justify using force in self-defense. A challenging aspect of this defense happens in cases where the victim claims self-defense for the killing of the abuser. Yet, the act happens after the assault or threat ends. It may even happen after the abuser falls asleep or several hours later.

First-Degree Murder Defenses: Accident

Killings committed by accident generally do not lead to murder charges. Instead, the state may charge involuntary manslaughter. If the accidental homicide took place during the commission of certain felony crimes, it can fall under a state's felony murder rule. In that case, the state might pursue first-degree or second-degree murder.

To succeed with an accident defense to a murder charge, the defendant will try to prove there was no intent to cause harm. This defense will be stronger if the defendant was otherwise engaged in legal activity. It may depend on how a state law defines acts of recklessness or criminal negligence.

First-Degree Murder Defenses: Insanity

Mental illness and legal insanity are not the same thing. There are many types of mental illness that, even when disabling, do not rise to insanity. Also, a finding that a defendant is incompetent to stand trial is not a finding of insanity.

Courts may determine that a defendant is mentally incompetent to stand trial. This means the defendant cannot understand the nature and consequences of a trial. It may also mean that the defendant cannot communicate with their attorney to aid in their defense. When this happens, the court may confine the defendant to a mental health facility until they are competent to stand trial.

Most states recognize an insanity defense in cases of first-degree murder. States that don't recognize an insanity defense still account for it in other ways (except Kansas).

Legal insanity, as defined in most states, consists of:

  • They are cognitively unable to appreciate the quality of the act committed. For example, a person with a mental defect may believe they are striking out at a demon rather than bludgeoning a person.
  • They are unable to realize that the act they are committing is legally or morally wrong (from a societal, not a personal view).

In some states, a defendant with a mental disorder that affects impulse control can use the insanity defense. They must show they did not have control over their own will or faculties. This lack of "volition" was a crucial element in the case of would-be presidential assassin John Hinkley Jr. After the verdict of not guilty by reason of insanity in the Hinkley case, many expressed concern. Efforts to reform the insanity defense spread throughout the U.S.

The Insanity Defense Reform Act of 1984 requires that the defense prove insanity by "clear and convincing evidence" in federal cases. It prevents direct testimony from expert witnesses on whether the defendant was insane. Experts give evidence of defendants' mental illness and abilities. This means that the judge or jury is the final fact-finder for insanity.

Pleading insanity does not let someone walk free for a murder they committed while impaired. Almost all defendants acquitted of murder by reason of insanity face institutionalization, often for long periods. Making successful use of an insanity defense requires good legal counsel. As the law related to insanity claims differs in each state, a defendant must have an attorney well-versed in defense strategies in this area.

Mitigation or Partial Defense of First-Degree Murder Charges

A partial defense to a murder charge does not acquit a person of their crime but reduces the crime to a lesser offense.

Infidelity and the Crime of Passion

Infidelity is still a mitigating factor in some states. A married person comes home, finds their partner in bed with another, and kills either the spouse or the paramour. Later, they may see their charges reduced to manslaughter on a claim their actions took place "in the heat of passion" provoked by the infidelity.

Killings committed in the "heat of passion" cannot be premeditated. They must represent a spontaneous reaction. Some states have adopted the more modern standard of "extreme mental or emotional disturbance" and will consider whether a reasonable person would likely experience similar disturbance in the same situation. Typically, this defense is only available if the killing is in immediate response to the provocation. It cannot appear as an act of revenge or some other reason.

Yet, modern society has great debate over laws that allow such exceptions. For example, the Massachusetts Supreme Court recently upheld a man's murder conviction in which he claimed the victim's statement of infidelity provoked his assault.

In Commonwealth v Ronchi, the defendant claimed his pregnant girlfriend told him he was not the father of the child she carried. She was due to deliver in one week. The court acknowledged that in most circumstances, words alone do not provide enough provocation for manslaughter. Yet, Massachusetts law allows an exception for words that convey "inflammatory information" to the defendant. The trial judge gave a manslaughter instruction, but the jury followed the state's argument. It disregarded the defendant's theory. It convicted him on two counts of first-degree murder.

The defendant claimed the court should use its authority to overrule the jury and find manslaughter and not murder. The court declined to do so. It decided that the time had come to end the state's prior rulings on oral disclosure of infidelity as a basis for enough provocation. The court concluded the infidelity exception relied on a "shaky, misogynistic foundation." It said that "oral discovery of infidelity no longer satisfies the objective element of something that would provoke a reasonable person to kill his or her spouse."

Duress or Emotional Distress

Likewise, some state laws allow defendants to claim that duress or extreme emotional distress reduces culpability. It can provide a partial defense to murder. Many state laws permit a person to plead "provocation" — that they were provoked to intense fear or anger by the victim's actions, even if the killing was otherwise unjustifiable. This is like the infidelity defense.

A disturbing version of this duress claim is the "gay panic" or "trans-panic" defense. A defendant claims a sudden discovery of a companion or dating partner's gender expression or sexual orientation caused an immediate response. They claim this justified or mitigated violence or killing. Many argue that this twist on emotional distress runs afoul of the "reasonable person" standard. In 2014, California banned using gay or transgender bias in "sudden quarrel or heat of passion" under its voluntary manslaughter law. Since that time, several more states have followed suit.

More Questions About First-Degree Murder Defenses? Get Legal Help

First-degree murder is the most serious criminal offense. Homicide charges of any kind carry harsh penalties. Anyone charged with a criminal homicide offense has the right to a legal defense. Consider talking with a local criminal defense attorney to learn more today.

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