What is Latent Fingerprint Detection?

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### What is Latent Fingerprint Detection? Latent fingerprints are invisible marks left by a person's finger that aren't visible to the naked eye. Forensic investigators use special equipment or substances to make these prints visible. One of the most common methods is using fingerprint powder. A person's hands and feet always have a fine film of oil, sweat, and other compounds on their surface. Whatever a person touches leaves behind traces of these substances, which creates a fingerprint that reflects the small ridge lines of the finger. When fingerprint powder is sprinkled over an affected area, the powder adheres to the oil, sweat, or other materials left in a fingerprint. This makes the fingerprint visible. Forensic scientists and law enforcement can then collect information about the fingerprint that helps identify the person who left it. ### Fingerprints in Crime Scene Investigation After crime scene investigators photograph the scene, they dust all surfaces with fingerprint powder to ensure they don't miss any potential evidence. When fingerprints are found, they're photographed, transferred to clear tape, and placed on a fingerprint card. After fingerprints are recovered from a crime scene, they're scanned into a criminal database to determine if there's a possible match, and kept on file for future matches. In the United States' national database for fingerprints is the Integrated Automatic Fingerprint Identification System (IAFIS). This system holds over 47 million fingerprint records and can match any fingerprint entered into it with any existing fingerprint in the database. Criminals are often fingerprinted to establish these records, and citizens may be fingerprinted during routine background checks. Latent fingerprint examination is a crucial part of crime scene investigations. Often, a criminal will touch surfaces at the crime scene with their bare hand, leaving behind a tell-tale fingerprint. Since each person has a unique fingerprint, investigators can match latent fingerprints found at the crime scene with a person in law enforcement databases to find the person responsible for the crime. Sometimes, fingerprints can be left not only from natural oils and sweat but also from other substances present at the crime scene. This can include blood, bodily fluids, or foreign substances. When this is the case, the fingerprint can indicate both the person responsible for the crime and what physical substances were present.