Fingerprint identification
Fingerprint identification is a well-established method used primarily in criminal investigations to link suspects to crime scenes. This technique relies on the unique patterns of friction ridges found on the fingers, palms, and feet, which are formed during fetal development and remain unchanged throughout a person's life. Each individual's fingerprints fall into three basic categories: arches, loops, and whorls, with additional subclassifications that enhance identification accuracy.
The process of fingerprint identification involves examining minutiae—specific characteristics like ridge endings and bifurcations—to ensure precise identification. Various types of prints can be collected, including visible patent prints, latent prints that require development, and plastic prints found on softer materials. Advanced technologies, such as the Automated Fingerprint Identification System (AFIS), allow law enforcement to efficiently search and match fingerprints against a vast database.
The application of fingerprint analysis can be critical in solving crimes, as demonstrated by its use in linking a suspect to a series of burglaries through footprint analysis. While gloves may prevent leaving fingerprints, investigators can still identify suspects through other trace evidence, underscoring the comprehensive nature of fingerprint identification in forensic science.
Fingerprint identification
SIGNIFICANCE: Fingerprint identification is one of the longest-established and most certain methods of identifying criminal suspects and linking them to crime scenes.
Friction ridge characteristics are located on the fingers, palms, and feet of the human body. The raised ridges and furrows on tips and at the end of the first joint of the fingers have identified people for centuries. Fingerprint patterns are unique to individuals; even identical twins do not have identical fingerprints. Fingerprint patterns form in the third fetal month of human development and remain the same until death and advanced decomposition.
Ridges rise above furrows to form specific patterns that are unique to each person. Fingerprints fall into three basic patterns: arches, loops, and whorls. Subclassifications further divide the basic patterns. The pores in the skin secrete a residue that leaves traces of latent fingerprint impressions. After a person has touched a nonporous surface like glass, patent prints are visible to the eye. Plastic, or indentation, prints may be found on soft surfaces such as putty. Invisible latent prints require development with laser, powders, and chemical techniques.
Fingerprint pattern interpretation assists in the classification, searching, and suspect elimination processes. The analysis of fingerprint minutiae, such as ridge endings, dots, islands, bifurcations, and other features, allows for the specific identification of a person. Comparison of fingerprint minutiae to an individual fingerprint creates a means of personal identification.
Elimination prints help identify family members and others who have legitimate access to the crime scene. Occasionally, witnesses or police officers will touch an object at the scene of a crime. Elimination prints help isolate those of the suspect.
Developing Fingerprints
Before beginning the collection process, examiners photograph fingerprints in place, whether the prints are visible, latent, or plastic. This procedure provides a permanent record and protects the fingerprints from any damage that may ensue as a result of the collection process. When searching for latent prints at a crime scene, examiners proceed in the least intrusive manner possible. They apply nondestructive resources to the print surface, such as lasers or a long-wave ultraviolet light source. Occasionally, a simple pen light with an oblique angle may reveal patent or latent prints. Physical and chemical methods may follow, depending on the surface.
The use of dusting powders, chemicals, and lifting applications presents a health hazard to investigators. Protective safety glasses are required for viewing prints with lasers and other light sources. Examiners wear respiratory masks and rubber gloves when applying fingerprint powder and other chemicals. When possible, this work is done in a well-ventilated area with a fume hood.
Fingerprint Computer Applications
The Federal Bureau of Investigation (FBI) maintains the national fingerprint database. State and municipal law-enforcement agencies maintain independent fingerprint record systems. Automated Fingerprint Identification System (AFIS) technology has the ability to search for individual fingerprints. This electronic database links suspects with their fingerprints. The FBI’s Integrated Automated Fingerprint Identification System (IAFIS) permits state and local examiners to search other state fingerprint databases. These database files contain prints of known offenders and forensic files of unsolved cases, which contain unknown fingerprints. The purpose of these forensic files is to link offenders to unsolved cases.
Formerly, searching record systems for single fingerprints could take years. The old Henry system and the former FBI extension system required all ten fingerprints for a successful search and match. As criminals rarely leave ten perfect prints at the scene of a crime, successful matches were an exceptional event in the absence of a known suspect.
Investigative Application
In one application, police were investigating serial burglary cases in a suburban community. The fingerprint expert dusted for traces of the burglar’s prints. The search produced only footprints, and the same footprint patterns emerged at every case location. The preliminary and follow-up investigation centered on one known female burglar. She specialized in jewelry thefts, breaking and entering in the daytime. The offender lived less than three miles from all the crime scenes.
The fingerprint examiner obtained footprint impressions from the suspect and compared them to footprints taken from each burglary location. The expert matched twenty-four minutiae ridge characteristics from the burglar’s feet to thirty other burglaries. The match involved basic minutiae ridges, such as ridge dots, endings, islands, and bifurcations. Comparisons provided a positive identification of the suspect as the one who committed the burglaries. During the subsequent interrogation process, the burglar revealed that she had worn gloves to avoid leaving fingerprint trace evidence. Furthermore, she had removed her shoes to avoid shoe impressions. Although wearing gloves did avoid a fingerprint match in the AFIS and IAFIS databases, the barefoot burglar overlooked the possibility that her foot impressions would exhibit the same points of identification as her fingers.
Bibliography
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"The Integrated Automated Fingerprint Identification System." Federal Bureau of Investigation, ucr.fbi.gov/fingerprints‗biometrics/biometric-center-of-excellence/files/iafis‗0808‗one-pager825. Accessed 5 July 2024.
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