Murder in United States law

In the United States, the law for murder varies by jurisdiction. In many US jurisdictions there is a hierarchy of acts, known collectively as homicide, of which first-degree murder and felony murder are the most serious, followed by second-degree murder and, in a few states, third-degree murder, which in other states is divided into voluntary manslaughter, and involuntary manslaughter such as reckless homicide and negligent homicide, which are the least serious, and ending finally in justifiable homicide, which is not a crime. However, because there are at least 52 relevant jurisdictions, each with its own criminal code, this is a considerable simplification.

Sentencing varies widely depending upon the specific murder charge. "Life imprisonment" is a common penalty for first-degree murder, but its meaning varies widely. Capital punishment is a legal sentence in 27 states, and in the federal civilian and military legal systems, though eight of these states and the federal government have indefinitely suspended the practice. The United States is unusual in actually performing executions, with 34 states having performed executions since capital punishment was reinstated in 1976. The methods of execution have varied, but the most common method since 1976 has been lethal injection. In 2019 a total of 22 people were executed, and 2,652 people were on death row. The federal Unborn Victims of Violence Act, enacted in 2004 and codified at 18 U.S. Code § 1841, allows for a fetus to be treated as a victim in a crime. Subsection (c) of that statute specifically prohibits prosecutions related to consented abortions and medical treatments.

If murder is committed within the borders of a state, that state has jurisdiction, and in a similar way, if the crime is committed in the District of Columbia, the D.C. Superior Court (the equivalent of a state court in the District) retains jurisdiction, though in some cases involving U.S. government property or personnel, the federal courts may have exclusive jurisdiction. If the victim is a federal official, an ambassador, consul, or other foreign official under the protection of the United States, or if the crime took place on federal property or involved crossing state borders, or in a manner that substantially affects interstate commerce or national security, then the federal government also has jurisdiction. If a crime is not committed within any state, then federal jurisdiction is exclusive, for example vessels of the U.S. Navy or the U.S. Merchant Marine in international waters and U.S. military bases worldwide. Recently, the Supreme Court, in the McGirt decision, reaffirmed that major crimes within the reservation boundaries of Native American tribes, for which a tribal member is suspected, must be investigated and prosecuted by the federal, not state, government. Federal penalties will apply if found guilty.

In addition, murder by a member of the United States Armed Forces of a prisoner while under custody of the United States Armed Forces is in violation of Article 118 of the Uniform Code of Military Justice and can result in the perpetrator being tried by a general court-martial, subjecting to certain types of jurisdictions within its own borders or with foreign nations. Jurisdiction over the crime of murder can be complex as a result of the principle of "dual sovereignty" that is part of federalism. In cases where a murder involves both state and federal jurisdiction, the offender can be tried and punished separately for each crime without raising issues of double jeopardy, unless the court believes that the new prosecution is merely a "sham" forwarded by the prior prosecutor. In the United States there is no statute of limitations on the crime of murder.

The first division of the general crime of murder into graded subcategories (first degree is worst) was enacted into the law of Pennsylvania in 1794. This enactment is often explained in terms of a desire to narrow the scope of application of capital punishment in that state and in the other states which subsequently graded murder into "first" and "second" degrees. The English common law, which had been received into the laws of the U.S. states, at the time applied capital punishment to a large number of crimes; as a result, states statutorily divided the crime of murder into first and second degrees, and began applying capital punishment only to criminals convicted of first-degree murder. By 1953, three states—namely Florida, Minnesota, and Wisconsin—had further created the subcategory of third-degree murder. States have adopted several different systems for classifying murders by degree. The most common separates murder into two degrees (first- and second-degree murder), and treats voluntary and involuntary manslaughter as separate crimes that do not constitute murder, instead of third-degree murder.

The Model Penal Code classifies homicides differently, without degrees. Under it, murder is any killing committed purposely and knowingly, even if it is a crime of passion murder without malice aforethought, manslaughter is any killing committed as a result of recklessness (also known as depraved-heart murder), and negligent homicide is any killing resulting from negligence. Some states classify murders differently. In Pennsylvania, first-degree murder encompasses premeditated murders, second-degree murder encompasses accomplice liability, and third-degree serves as a catch-all for other murders. In New York, first-degree murder involves "special circumstances", such as the murder of a police officer or witness to a crime, multiple murders, or murders involving torture. Under this system, second-degree murder is any other premeditated murder. The New York statutes also recognize "murder for hire" as first-degree murder. Texas uses a scheme similar to New York's, but refers to first-degree murder as "capital murder", a term which typically applies only to those crimes that merit the death penalty. Some states, such as Florida, do not separate the two kinds of manslaughter.

Under the common law, an assault on a pregnant woman resulting in a stillbirth was not considered murder. Remedies were limited to criminal penalties for the assault on the mother and tort action for loss of the anticipated economic services of the lost child, for emotional pain and suffering, or both. With the widespread adoption of laws protecting unborn life, the assailant could be charged with that offense, but the penalty was often only a fine and a few days in jail. A number of states have passed "fetal homicide" laws, making killing of a fetus murder; the laws differ about the stage of development at which the fetus is protected.

After several well-publicized cases, Congress in 2004 passed the Unborn Victims of Violence Act, which specifically criminalizes harming a fetus, with the same penalties as for a similar attack upon a born human being, when the attack would be a federal offense. Most such attacks fall under state laws; for instance, Scott Peterson was convicted of killing his unborn son as well as his wife under California's pre-existing fetal homicide law.