Solving crime at the ‘fingertips’

Hence, fingerprints are permanent and remain on objects and niches at a crime scene, and are treated as evidence.
Solving crime at the ‘fingertips’
pic credit: Daekow

Fingerprints are a unique anatomical identification signature of human beings, and have been considered the gold standard for personal ID in forensic science globally, for over a century. Whenever a physical crime happens, such as theft or murder, one of the first articles of proof to be collected from the crime scene are fingerprints, which could directly point towards the existence of a person or potential suspect at that spot during the time of the crime.

Long before the arrival of DNA analysis and other cutting-edge digital tools to aid forensic investigation, fingerprints provided much needed tangible evidence to link a suspect to a crime. Argentina became the first nation to rely solely on fingerprints as a method of individualisation. In 1892, Argentine police discovered a bloody fingerprint on a door frame, at a crime scene, and analysed it to identify a murderer. That same year, many police departments around the world began to maintain fingerprint records. Logic suggests that usually no crime can be committed without hands. Hence, fingerprints are permanent and remain on objects and niches at a crime scene, and are treated as evidence.

Fingerprints are something which cannot be erased easily, and inadvertently end up wherever an individual has been; and because of which, play an important role in solving a crime. Prints are left on anything that is touched and they cannot be covered up because human fingerprints are unique, difficult to be altered or imitated, and durable over a lifetime, making them suitable as lifelong markers of human identity. Fingerprints are readily used by police to identify individuals – either to link them to a crime or to identify those incapacitated or deceased.

The major types of fingerprint patterns can largely be classified as arch, loop, whorl, and others. The latter type includes three subtypes – twin loop, random loop, and lateral pocket loop – which are subsumed under other type because of their low frequencies.

Glass in hand

Whenever a crime is reported, the police inform the forensic team, which gets to work by searching for fingerprints in a systematic manner. Every part of the crime scene is mapped and marked – especially the entry and exit points (doors and door handles), seating, furniture, cupboards, and other objects. If a weapon is found, it is expected to contain some fingerprints. The fingerprints found at the scene of occurrence are divided into three parts – Latent, Patent and Impressed.

Unlike patent fingerprints left in a substance (like ink or blood) or impressed fingerprints left in a soft material (like wax), latent prints are invisible without specific enhancement techniques. A magnifying glass helps locate the quality of fingerprints. A Polilight System aids in searching for fingerprints, with the strong radiation beams leading from UV to IR detecting latent prints.

Special powders are used as the medium to reveal latent prints, which are then gently dusted off with a brush made of fibreglass or feathers, and the print is collected on a transparent adhesive tape or film. Later, fingerprint examiners use the ACE-V (analysis, comparison, evaluation and verification) method to determine each print. Also, a lot of computer tools and software have made the fingerprint identification process more seamless and accurate today.

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