Forensic Fingerprint Analysis

With the aid of forensic analysis, law enforcement officials are able to solve crimes with little more than fingerprints as evidence. Based on the presumption that no two fingerprints are alike, even if taken from different fingers of the same individual, fingerprint identification techniques are employed in criminal investigations, citing 10 to 50 matching points to illustrate a positive identification.

Extraction Process

Fingerprint samples can be extracted in a number of ways, including with the aid of a crime scene dusting kit, a biometrics device or even a photograph. Dusting for prints commonly relies on powder made from charcoal, titanium or aluminum. This powder adheres to oil contained within fingerprints, allowing investigators to capture a print for use in forensic analysis. Biometrics devices capture fingerprints with the aid of advanced technology and are usually used by law enforcement agents to process subjects into the criminal justice system. High-clarity photographs have been used as instruments of fingerprint identification in situations where evidence from a crime scene has either been corrupted or destroyed.

Ridge Analysis

Ridge configurations within a fingerprint pattern render each fingerprint unique and identifiable through expert analysis. Three features within a print pattern that help experts to make a positive fingerprint identification are loops, whorls and arches. Loops are ridges that enter from one side of a finger and curve to exit in the same direction from which they originated. Whorls are circular ridges that also typically extend from one side of a finger to another. Arches are similar to loops; however, they enter one side of a finger, rise in the finger's center and exit at the other side of the finger without curving toward their point of origin. Experts carefully analyze a sample print's characteristics, observing the presence of each of these patterns.

Database Comparison

With the aid of computerized fingerprint identification systems, forensic analysts and law enforcement officials are able to compare specific samples to a database of known prints that have been extracted from a general population. The Federal Bureau of Investigation boasts that the criminal master file of its Integrated Automated Fingerprint Identification System contains more than 55 million subjects.

Chain of Custody

Fingerprints, which are vital pieces of evidence that can easily be tainted, must be carefully handled in order to retain value while being processed in a forensic investigation. The chain of custody process serves to document the processing of a fingerprint during a criminal investigation, step by step. Law enforcement officials are held accountable to complete paperwork related to processing of this evidence, and such paperwork may be referred to at a later date if the fingerprint becomes corrupted.

Reliability

Due to a lack of definitive proof that fingerprints are indeed unique patterns that suffer minimal degradation over time, critics of forensic fingerprint analysis contend that results gleaned through analysis are unreliable. Law professors Jane Moriarty and Michael Saks argue that inconsistent standards of analysis, expressed across a number of unrelated agencies, result in potentially faulty methods of fingerprint identification that rely less on methods of science than they do subjective speculation.

References

• Vermont Forensic Laboratory Physical Comparison Unit
• Integrated Automated Fingerprint Identification System
• Forensic science under siege; Kelly Pyrek; 2007