Forensic Science: Myth vs Fact

Crime Scene Investigation

Myth: A single investigator trained in forensics can collect and analyze all evidence from a crime scene.

Fact: Crime scene investigation and analysis requires a team of knowledgeable experts to collect and process evidence. Because of their training and expertise, investigators and analysts tend to specialize in a particular forensic discipline such as fingerprints, firearms or DNA analysis. The process is tedious and time?consuming because investigators must collect all possible evidence without knowing in advance what is relevant to an investigation. In a separate step, only highly trained laboratory?based analysts from various disciplines can conclusively examine crime scene evidence and report their findings.

Alternate Light Source (ALS)

Myth: With a blue light, investigators can detect the presence of blood at a crime scene.

Fact: While television programs often depict the use of a special light to detect blood at a crime scene, the use of Luminol alone in a dark room without special lighting allows visual detection of the presence of blood. Other bodily fluids, such as saliva and semen, become fluorescent under an ALS.

DNA Analysis

Myth: Advanced DNA analysis automatically identifies an individual within minutes.

Fact: DNA analysis takes several hours for even simple cases, although a laboratory typically takes 30 days or more to complete DNA testing. In addition, the FBI’s Combined DNA Index System (CODIS) stores no personal data with its 7.5 million records. To confirm identity, analysts search other databases containing information about convicted offenders, unsolved crimes and missing persons at the local, state and national levels. For more information, visit

Drugs and Explosives Testing

Myth: A trained crime scene investigator can usually identify an unknown powder by sight, smell or taste.

Fact: Contrary to television portrayals, crime scene specialists never taste an unknown substance to determine its composition because of the danger posed by the potential presence of poisons. Instead, investigators are armed with hand?held, portable kits to conduct preliminary, presumptive testing of unknown powders in the field. Only confirmatory analysis with sophisticated instrumentation can conclusively determine the components of a sample powder submitted as part of an investigation.

Digital Evidence

Myth: The Internet Protocol (IP) address can identify who sent an e?mail.

Fact: An IP address is analogous to a telephone number. While both numbers are uniquely assigned, investigators can determine only the person who pays for the IP address or telephone number by using public records and the legal process. Whether tracking an IP address to a public access router or to a private home, investigators still need to use old?fashioned police work to place a suspect “at the keyboard.”


Myth: You can always match a bullet with the gun that fired it.

Fact: The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) maintains the National Integrated Ballistics Information Network (NIBIN), which allows law enforcement agencies to scan and compare digital images of the firearm markings on bullets and cartridge casings. However, if a gun has been modified after firing or if the bullet is badly damaged, the bullet will no longer match the barrel and a link cannot be confirmed. Frequently, cartridge casings provide more information than the actual bullet fired.

SOURCE: National Forensic Science Technology Center (NFSTC) –

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