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First Degree Murder Defenses

A charge of first-degree murder could be fought with many possible defenses. This article discusses the defenses and defense strategies that may be used in first-degree murder cases. Some of these may be a complete defense, while others may mitigate sentencing or lead to a reduction of charges to second-degree murder or manslaughter.

First-Degree Murder Defenses: Mistaken Identity

In first-degree murder cases, as well as other homicide crimes, defendants often argue mistaken identity. That is, that the prosecution has charged the wrong person with the killing. Often the defendant will have an alibi and evidence to support their claim that they were somewhere else at the time of the killing.

Other arguments in a mistaken identity defense include challenges to evidence placing the defendant at the scene of the crime. This can include challenges to witness identification as well as challenges to forensic evidence. The defense attorney may move to suppress evidence that was gathered improperly.

A mistaken identity defense may also point to evidence implicating another possible suspect, but courts do not require defendants to do so.

First-Degree Murder Defenses: Failure to Prove the Elements

First-degree murder is a very specific crime with specific elements, each of which must be proven beyond a reasonable doubt. There are variations in state laws, but the model penal code definition of murder (criminal homicide) requires:

  • The killing of another person
  • Committed purposely or knowingly
  • Or committed recklessly under circumstances of extreme indifference to human life. (If the murdered was engaged in, or an accomplice to, a crime of robbery, burglary, arson, kidnapping, rape, or escape from law enforcement or incarceration, it is presumed that their actions were reckless and indifferent.)

If one of these elements is missing, the accused should not be charged with the crime of first-degree murder. They may be charged with second-degree murder or manslaughter.

While the defense may argue that one or more of these elements was not present, the defense does not have to do so. It is the prosecutor's burden to prove each one of these elements to a jury.

First-Degree Murder Defenses: Justification

There are a number of ways that a defendant can argue that the killing of another person was justified and should not be considered first-degree murder. This article will look at some of the most common justifications: self-defense, defense of others, and exercise of duty. There are more esoteric justifications, such as necessity or choice of evils, but they are seldom applicable to homicide cases.


The most common justified homicide is killing is in self-defense. To succeed, a defendant arguing self defense must show that the killing was a reasonable use of force to resist a reasonable fear of death or bodily harm. Mere words or insults would not suffice.

The defendant cannot have instigated the threatening situation. The degree of force used must be proportional to the perceived threat. And the defendant's reaction to the threat cannot take place after the threat of death or bodily harm has passed.

Many states require that the defendant attempt to retreat or avoid danger, if possible, before resorting to the use of deadly force. These states do not allow self-defense if it is shown that the killer could have safely avoided the threat to by retreating. States differ in the degree to which they require an attempt to retreat from a threat, but no state requires retreat from a threat inside one's home.

According to the National Conference of State Legislatures (NCSL), more than 25 states have “stand your ground" laws. These statutes impose no duty to retreat, and instead encourage violent confrontation of threats. In Florida, the "stand your ground" law is well known because it allowed George Zimmerman to be acquitted for the killing of 17-year-old Trayvon Martin, a black teenager walking home at night.

Battered Woman Syndrome

Battered woman syndrome has been used since the 1970s to mitigate the criminal charges brought against women accused of killing their abusers. The term refers to a pattern of psychological and behavioral symptoms frequently seen in women who have been living in abusive relationships.

Battered Woman Syndrome is not a specific legal defense but is used to substantiate claims of self defense or insanity. A challenging aspect of this defense occurs when the act of self defense — the killing of the abuser — does not occur at the same time as the assault or threat that led to it. It may be the case, for example, that a battered woman waits until her abuser is asleep before killing him.

Defense of Others

Defense of others can also be used as a defense for justifiable homicide. A person can defend another person from harm if they reasonably believe that intervention is justified and that the person being aided could have had a legitimate claim for self-defense. The use of force must be timely and proportional to the threat faced. The perceived threat of death or bodily harm must be reasonable. Basically, if a threatened person would have been justified in using deadly force to protect themselves, someone else 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. If an officer kills someone in the exercise of duty, without unlawful intent, recklessness, or negligence, that killing generally does not constitute murder, let alone first-degree murder.

State like California have laws that protect public officers and those acting under their command when a killing results from an officer exercising their legal duty, as long as excessive force is not used.

It should be noted that there is no right to use lethal force to resist law enforcement.

Prevention of a Crime

Some state statutes allow for those who are not in law enforcement to use force to prevent certain dangerous types of felony crimes, such as robbery, kidnapping, arson, and burglary.

Texas allows noteworthy leniency. Its statute authorizes the use of deadly force to prevent misdemeanor theft at night. This was affirmed by Surges v. State in 1920 when the highest court in Texas overturned a murder conviction for a man who shot a suspected whiskey thief at night.

First-Degree Murder Defenses: Insanity

It's important to keep in mind that mental illness and legal insanity are not the same thing. There are many types of mental illness that, even when disabling, do not impair a person's moral compass.

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

Some people are determined to be mentally incompetent to stand trial. They cannot understand the nature and consequences of a trial and they cannot participate in their own defense. They are typically confined to a mental health facility until they are competent to stand trial.

Legal insanity, for purposes of determining criminal liability, is defined in most states as:

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

In some states, the insanity defense can be used by defendants with a mental disorder that affects impulse control if they can show that they did not have control over their own will or faculties. This lack of "volition" was a key element of the insanity defense of famed would-be presidential assassin John Hinkley, Jr. After his acquittal, reform of the insanity defense spread throughout the U.S., making it more difficult to get a verdict of not guilty by reason of insanity alone. The Insanity Defense Reform Act of 1984 requires that the defense prove insanity by "clear and convincing evidence" and prevents expert witnesses from testifying whether the defendant was insane or not, limiting their effectiveness to the defense. Some versions of the insanity defense do not result in a not-guilty verdict, but instead in reduced criminal liability and lesser punishments. These include:

  • Hallucinogenic delusion (even if self-induced by use of psychotropic drugs),
  • Post-traumatic stress disorder (PTSD)
  • Postpartum psychosis
  • Diminished capacity (another name for the oft-misunderstood "Twinkie defense") - the inability to form criminal intent due to incapacity.

Pleading insanity does not let someone walk free for a murder that they committed while impaired. Almost all defendants who are acquitted for murder by reason of insanity are institutionalized, often for decades, rather than released to the public.

Mitigation or Partial Defense of First-Degree Murder Charges

A partial defense to a murder charge is a defense that does not acquit a guilty person of the crime they have committed but reduces the crime to a lesser offense.

Adultery and the Crime of Passion

Adultery continues to be a mitigating factor in some states. If a married person comes home and finds their partner in bed with another and shoots either the spouse or the paramour, they could see their charges reduced to manslaughter by pleading that their actions took place "in the heat of passion" because they were provoked by the adultery.

Killings committed in the "heat of passion" must not be premeditated, but represent a truly 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, not as an act of revenge or some other reason.

Duress or Emotional Distress

Some states allow defendants to claim that duress or extreme emotional distress reduce culpability and provide a partial defense to murder. Most states allow a person to plead "provocation" - that they were provoked to intense fear or anger by the victim's actions, even fi the killing was otherwise unjustifiable (similar to the adultery defense).

A disturbing version of this is the "gay panic" or "trans panic" defense. A defendant claims that the sudden discovery of a dating partner's gender expression or sexual orientation justify violence or killing. This twist on the emotional distress plea seems to run afoul of the "reasonable person" standard. As a result, eight states have banned the use of this defense, and equality advocates call for its complete abolition.

Accidental Killing

Killings committed by accident generally do not constitute murder but are charged as voluntary manslaughter or involuntary manslaughter. However, if the accidental homicide took place during the commission of a crime or with criminal intentions, it could be considered first-degree or second-degree murder.

Consider this tragic example: a teenager is playing around with a parent's gun and, believing it to be unloaded, points it at a friend and pulls the trigger. The teen lacked any intent to harm, but perhaps was negligent. A defense attorney could argue for reduced charges. In many states, the parent who leaves a loaded gun accessible to a child is more likely to face tough penalties for reckless or negligent homicide.

Incidents like hunting accidents can end with the "guilty party" completely exonerated of murder charges.

Get Legal Help with Your First-Degree Murder Defense

The most serious crime a person can be accused of is first-degree murder. The stakes are high and the penalties can include life imprisonment or the death penalty. Get the best possible legal defense. Contact a local criminal defense attorney to learn more about how to defend against a first-degree murder charge.

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