First-degree murder defenses are grouped into two categories. Some defendants claim innocence, while others admit to the act but argue that it was not first-degree murder. The latter group of defendants can assert self-defense, legal incapacitation or justification. A Houston Attorney may argue that a client’s act does not prove all of the elements of first-degree murder, and jurisdictions often have different defense rules. Below is a list of the most common defenses used in first-degree murder cases.
Mistaken Identity Cases
In a first-degree murder case, defendants and their attorneys often argue that the prosecutor has accused the wrong person. In these mistaken identity cases, the defendant often offers an alibi. Evidence putting the defendant at the crime scene can be challenged, as can forensic evidence and witness identification. A defense of mistaken identity can offer evidence implicating other suspects, but the court does not require it.
Justifiable Homicide
Not every homicide meets the definition of a crime, let alone a first-degree murder. Certain grounds justify the killing of one human being by another. Common legal justifications for homicide include self-defense and the defense of other people.
- For a self-defense claim to be successful, the defendant must prove that the death resulted from the use of force sufficient to resist the threat of bodily harm or death. The defendant must not have instigated the situation, and the force and threat must be proportional.
- The proportional and reasonable defense of other people can justify some killings. The requirements are the same as for a self-defense case; the threat must be reasonable, and the force must be proportional.
Fulfilling a Duty
Some killings by public and law enforcement officers may be justified. If a police officer kills another person in the line of duty and without recklessness, negligence or unlawful intent, the killing does not meet the definition of murder.
Accidents
An accidental killing that occurs in the course of a lawful activity is not a murder. Some of these killings result in manslaughter charges, but first- and second-degree murder laws do not apply unless the killing happened during a felony.
The Insanity Defense
Most jurisdictions allow insanity defenses to first-degree murder charges. However, strict rules apply. In most cases, insanity is defined as a defendant’s inability to distinguish right from wrong, or to appreciate the seriousness of the act.
