Whether or not a deceased person is a murder victim would appear to be a simple thing to determine. Presumably the primary deciding factor in determining if detectives are investigating murder cases would be the presence or lack of a murder victim, but the legal qualification for a crime's consideration as a murder case depends on several variables.
In his Commentaries on the Laws of England from the middle 18th Century, William Blackstone described murder cases as those cases in which a person who had full control of his mental facilities killed a person outside of war with explicit malice.
Malice is a difficult concept to prove in murder cases. There are four different circumstances used to determine if a murder victim died as a result of murder. The first is if the killer exhibited an intent to kill. Intent to kill can be determined if a deadly weapon is used. Deadly weapons in murder cases are defined as guns, knives, or a car if used to hit a person intentionally.
If a murder victim dies as a result of a killer's intent to inflict serious harm short of death, the prosecution and police may elect to pursue it as stringently as an intentional killing. If a murder victim has died because of a killer's reckless indifference to the high probability that death or serious bodily harm would be likely to result, then murder cases may be pursued.
Reckless indifference statutes also cover murder cases in which the murder victim died as a result of actions taken by the killer while under the influence of both legal and illegal drugs, or alcohol.
The fourth and final definition of malice in murder cases is referred to as felony murder. Felony murder covers instances when a murder victim dies while the killer was intending to commit a dangerous felony. Dangerous felonies include rape, burglary, arson, robbery, sodomy, and/or kidnapping. Assault is not considered a lesser included offense that can result in a felony murder charge because all murder cases involve an assault of some sort.
Murder cases which lack intent or malice are codified as manslaughter. In some jurisdictions there has been a movement to consider a fetus killed during the committing of another crime a murder victim. Under Californian law a fetus can be a murder victim even if the mother was legally able to abort the fetus as a result of Roe v. Wade.
A fetus that may not be a viable entity if it was separated from the mother at the time of the accused murder or would not be detectable due to being underdeveloped could still be considered a murder victim in cases prosecuted under these California laws.