Murder is often the most difficult crime to prove because the victim is unable to testify, at least not in the traditional sense of the word. With the advances in forensic science, however, during the the 20th century, a victim can provide a number of clues and murder evidence for law enforcement to use in apprehending and convicting the perpetrator. Among the various types of murder evidence are: fingerprint and impression evidence; blood, semen, hair, and other biological evidence; eyewitness or videotape evidence; and documentary evidence.
Fingerprints can be an excellent piece of murder evidence because no two sets of fingerprints are the same. Along with fingerprints, many other things can leave impressions that can be used as murder evidence, such as shoes or tires. Forensic experts are often able to take a cast made from an impression of a shoe or tire and determine what type of tire or shoe made the impression. An analysis of a shoe impression can often give investigators additional information, such as the shoe size and weight of the person wearing the shoe.
When a murder is committed, evidence from the perpetrator is frequently left behind. This is particularly true if a struggle ensued during the crime. As a result, murder evidence in the form of blood, hair, semen, or even nail clippings is often present at the crime scene or found on the body of the victim. Because much of the biological evidence found in a murder investigation consists of evidence that is unique to an individual, it can be the key to solving a murder or securing a conviction at trial.
Eyewitness evidence is clearly valuable in a murder investigation. While, in some cases, a witness may have been close enough to positively identify the suspect, it is more likely that an eye witness can only give general identifying information, such as height, weight, race, and sex. In today's digital age where there appear to be cameras on every corner, there is often video evidence that can be used to identify or rule out a suspect in a murder case as well.
Documentary evidence is often helpful in a murder case to provide a motive or to place a defendant in the area at the time of the murder. Financial gain is one of the most popular motives for a murder, which makes financial records prime murder evidence. Records of financial transaction, such as paying for something or withdrawing money at an ATM with a credit or bank card, can also place the suspect near the murder scene, or prove that the suspect was somewhere else at the time of the murder.