Homicide *is* murder.
Murder is homicide. Not all homicide is murder.
http://legal-dictionary.thefreedictionary.com/homicide
Homicide:
The killing of one human being by another human being.
Although the term homicide is sometimes used synonymously with murder, homicide is broader in scope than murder.
Murder is a form of criminal homicide; other forms of homicide might not constitute criminal acts.
These homicides are regarded as justified or excusable.
For example, individuals may, in a necessary act of Self-Defense, kill a person who threatens them with death or serious injury, or they may be commanded or authorized by law to kill a person who is a member of an enemy force or who has committed a serious crime.
Typically, the circumstances surrounding a killing determine whether it is criminal. The intent of the killer usually determines whether a criminal homicide is classified as murder or Manslaughter and at what degree.
(snip)