Everyone is unique. A trite line considering it has been said and heard over and over again by people across the world and time. But it is actually factual. The ridges on your palms and fingers can prove this. Amazingly, these ridges form patterns on your hands that are unique for every person. While it is known the world over that fingerprints are distinctive for every individual, few of us know about the way fingerprints are analyzed.
Fingerprints are formed when you touch a surface and leave an imprint of your unique ridge pattern. There are basically three types of fingerprints that are analyzed. These are:
- Latent prints. These are prints that were accidentally left in an area. This means that latent prints are commonly smudged or distorted. Because these prints are left unintentionally or by mistake, latent prints have less clarity than those prints taken when the conditions are controlled, i.e., the use of scanners to record fingerprints. There are many processing techniques used to allow visualization of latent prints. The more common ones are electronic, chemical and physical processing.
- Patent prints. This type of print occurs when the hand or fingers touch a foreign material, i.e., ink, and this foreign material is transferred onto a surface. Patent prints do not need any electronic, chemical or physical form of enhancement. What experts usually do is just photograph the area or the surface on which the prints are found.
- Plastic prints. A plastic print differs from a patent print in the sense that the material on which the impression is left usually takes the shape of the details of the ridges. Some of the common materials on which this type of print is left are candle wax, thick grease and semi-dried to dried ink. But the officials doing the crime scene investigation usually check the material for latent prints. In many cases, plastic prints also contain latent prints that are not directly visible to the normal human eye.
Investigations from crime scenes are used as evidence for prosecution. And since it is necessary for the suspect to be proven guilty beyond reasonable doubt, there are steps and methods taken when studying latent fingerprints. Latent prints, unlike DNA, are not accurate all the time. This is where a likelihood ratio comes in. You cannot simply disregard the probability of an individual having the same relative ridge arrangement as another. Unlike prints taken by a scanner, latent prints are relatively low in clarity. When used as evidence, the prosecution hypothesis and the defense hypothesis are both taken into consideration. The ratio of the probability of these two is the likelihood ratio.
But fingerprint analysis is not only used in criminal cases or as evidence for prosecution. With the advancements in biometric science, prints are used as identification for security purposes. For example, instead of using ID cards, some companies protecting sensitive data use biometric scanners to identify their employees. The more common electronic types are fingerprint and eye scanners.
Most countries with access to advanced electronics also use these systems in immigration. Cross checking of visa information also includes biometric information stored in databases that are available to many countries. This makes it possible to prevent the entry of an individual with a criminal record.