The use of fingerprints to prove that a specific person was present at a specific location or touched a specific object is known as forensic fingerprinting. This is usually done to prove guilt or innocence in criminal cases, but it has limited applications outside of that. Humans have ridges on their fingers that are usually distinct from one another. Humans leave fingerprints on almost everything they touch as a result of the oil and sweat on their hands. To prove identity, skilled forensic scientists can distinguish one person’s prints from another’s and then match the print to pre-existing records.
Small amounts of material are usually left behind when a person touches a surface. Because the hands and feet make the most contact with the surface, this material will conform to the ridges found there. This material is a key to the identity of the person who left it for a forensic fingerprinting expert. The problem is that, while nearly everyone’s fingerprints are unique, most prints will vary from time to time — it’s not uncommon for multiple people to have sections of ridges on their fingers that are nearly identical. The angle at which the print was created, the surface that was touched, and the pressure that was applied all have a significant impact on the print’s structure and design.
A person performing forensic fingerprinting will compare key points between prints to look for common factors in order to sift through this. Certain sections of a print will look the same as other prints, while others will not. Forensic fingerprinting can determine a likely match by comparing points on the finger that suffer the least distortion and those areas that match across prints.
Fingerprints are divided into four categories. A fingerprint exemplar print is a print that was taken specifically to be used as a fingerprint record. Because they are taken in a controlled environment using professional methods, these are usually the best prints available. Plastic prints are the other type of print that is popular. These prints are three-dimensional prints that have been perfectly preserved, such as an impression in clay or plaster.
The two least well-made prints are the most commonly used in forensic fingerprinting. A patent print is a fingerprint that can be seen without a magnifying glass. These prints are frequently created by touching a dirty or extremely clean reflective surface, such as a dusty car or a mirror. Under normal circumstances, latent prints are undetectable. To be visible, these prints require special powder or lighting conditions.