Murder is the unlawful killing of a person by another person. Murder is a serious crime that can result in criminal charges and severe consequences for the perpetrator. Most jurisdictions divide murder into degrees to indicate the level of culpability, with murder of the first and second degree being the most serious crimes. The degree to which a person commits murder is determined by their intention. Carefully planning how to kill someone, for example, is a sign of malice aforethought and will lead to more severe punishment than if the killing happens by accident during the commission of another crime. This concept is known as mens rea and is examined in homicide cases to determine guilt or innocence and appropriate repercussions.
Serial or mass murder, where one person kills a large number of people, also fall under the category of murder and are very high profile crimes. These can attract much attention from the media, as well as politicians and social activists, which can have a major impact on public opinion.
A key component of a good murder mystery is a sympathetic protagonist that readers can empathise with and who they want to see a happy ending for. Readers will also need to be kept guessing about who committed the murder and this can be achieved through clues and red herrings that point them in the wrong direction. These can be anything from physical evidence that appears to implicate a character but is later revealed to have been planted, to eyewitness testimony that is contradictory.