How Ridge Detail can assist in Crime Scene Investigations

In crime scene investigations, fingerprint identification is one of the oldest and commonly used ways of identifying people who have been present.

Since the late nineteenth century, fingerprint identification has been used by law enforcement agencies around the world to identify both suspected criminals and the victims of crime. Fingerprint detection is also used in the elimination of people from crime scenes (proving they were not there) and for identification purposes during elections.

Crime Scene Fingerprints

Fingerprints at a crime scene may be detected by using light, powders or chemicals. More complex techniques, usually chemical, are performed in specialist forensic laboratories to lift fingerprints from articles removed from the crime scene but these chemicals can also be used at the scene of crime should the need arise.

Patent and Latent Fingerprints

Fingerprints on surfaces can be described as either patent or latent. Patent fingerprints are left when a substance (like paint, oil, or blood) is transferred from the finger to a surface. Patent impressions are usually visible and usually need no enhancement. These type of fingerprints are easily photographed without further processing.

Latent fingerprints occur when the natural secretions of the skin (oil and perspiration) are left on a surface through contact, leaving an impression of the friction ridge detail of the finger or palm. In most cases, latent fingerprints are not visible. However, they are not invisible. Using available or oblique lighting on most surfaces will reveal the impression. These latent prints must be enhanced or developed to be fully seen and collected using lifting techniques or specialist photography. Some can be lifted at the crime scene with powders and brushes and others are enhanced in a forensic laboratory.

What is Fingerprint Identification?

Fingerprint identification (sometimes referred to as dactyloscopy or palm print identification) is the process of comparing questioned and known friction skin ridge impressions from fingers or palms to determine if the impressions are from the same finger or palm.

The lines on fingers, palms, and parts of feet are known as friction ridges, which humans use to help them grip rough surfaces, as well as smooth wet surfaces.

In forensics, friction ridge detail serves as a method of identification of an individual.

Fingerprint Classification

Every day fingerprints are collected all around the world by various organizations and law enforcement agencies and stored for a wide range of applications including forensics, access control, and driver license registration.

In order for the search time to match fingerprints to be reduced several systems of classification have been developed. Fingerprints are categorized in an accurate and consistent manner so that the examiner can easily search either manually or digitally through the database.

General Ridge Formations

Fingerprint classification is a technique to assign a fingerprint into one of the several pre-specified types already established in order to provide an indexing mechanism. Loop, Whorl and Arch and three of these types.

In the days before computerization replaced manual filing systems in large fingerprint operations, manual fingerprint classification systems were used to categorize fingerprints based on general ridge formations (such as the presence or absence of circular patterns in various fingers)

In the Henry system of classification used in most of the English-speaking world, there are three basic fingerprint patterns: Loop, Whorl, and Arch

The Fingerprint Database

The FBI manages a fingerprint identification system and database called IAFIS, which currently holds the fingerprints and criminal records of over 51 million criminal record subjects, and over 1.5 million civil (non-criminal) fingerprint records as do law enforcement agencies in most other countries. Some less enabled countries are starting to invest in AFIS technology unfortunately it is very expensive and really stretches the budget of these smaller nations. They still rely on the fingerprint examiner to manually examine the images lifted from the scene against the criminal records held on file or provided during the enquiry.

Fingerprint Identification

Every day fingerprint identification makes far more positive identifications of people worldwide than any other human identification procedure. There is some unhappiness about fingerprint identification, which probably stems from the fact that people try to put the conclusiveness of fingerprint evidence on the same level as DNA evidence. However, there is no doubt that fingerprints as an analogy of uniqueness has been widely scientifically accepted and it has been proved that no two people have the same fingerprints.

One of the reasons that fingerprints are such a good crime scene investigative tool for both inclusion and exclusion is because they are unique to each person. Even identical twins (who share DNA) do not have identical fingerprints.

The International Fingerprint Research Group (IFRG), which meets biennially, consisting of members of the leading fingerprint research groups from Europe, the US, Canada, Australia and Israel leads the way in the development, assessment and implementation of new techniques for operational fingerprint detection.