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Fingerprint Analysis and Identification

Author: Becky Li

Editors: Kevy Chen, Hwi-On Lee

Artist: Acey Li

In the stillness of a suburban night, a scream shatters the tranquility of silence, casting a dark veil on the neighborhood. In the commotion, a single fingerprint remains, quietly bearing witness to the events that unfolded. Like invisible ink on paper, each fingerprint leaves an unspoken story on every surface it touches. 

Investigators analyze fingerprints to help connect the crime to a person present at the scene, whether it's to identify an unknown victim or the perpetrator of the crime. The principles of fingerprint analysis begin with the unique ridges and furrows on your palms, toes, and fingers, which can be differentiated into three distinctive patterns: loops, whorls, and arches. Loops are prints that curl onto themselves to form an “O” shape. These prints are the most common, accounting for approximately 60 percent of pattern types. Whorls form spiral patterns, almost like a whirlpool, and can be further categorized into four groups: plain (concentric circle), double loop (2 loops that form an S-like pattern), accidental loop (irregularly shaped), and central pocket loop (loop with a whorl at the end). Lastly, arches are wave-like and can be classified as plain or tented arches (which rise more sharply than plain). 

The two premises of fingerprint identification are uniqueness and permanence. No two people have been found with identical fingerprints, even identical twins. Interestingly, each of your fingers has a unique fingerprint. Permanence refers to the principle that your fingerprint will be unchanged throughout your lifetime. Even if your skin is damaged or you attempt to remove your fingerprint, the new skin will grow back in the same pattern. 

Fingerprints can be collected with the help of numerous techniques. One example is patent printing, which consists of taking high-resolution photographs of visible fingerprints. These fingerprints usually result from the skin of your fingers being coated in foreign substances such as blood or paint. Another method is latent printing: dusting a smooth surface with a fingerprint powder and photographing the emerging prints. However, fingerprint powder may contaminate the fingerprint and hinder further analysis. To resolve this, an alternative technique is used with light sources, such as a laser or LED light, to examine surfaces. A third method is superglue fuming. Cyanoacrylate ester is an active ingredient in superglue, creating a vapor that polymerizes (forms a white residue) and sticks to any present prints, making them visible for investigators to analyze.

After obtaining the fingerprints, investigators will compare them to those in their national databases. The International Criminal Police Organization (INTERPOL) runs an international fingerprint database with an automatic fingerprint identification system (AFIS), containing over 220,000 fingerprints and 17,000 crime scene marks. This system allows authorized users to check these records from their national databases against AFIS to match fingerprints from the crime scene to those in the databases. 

Analysts will first use the general patterns (loop, whorl, or arch) to make preliminary comparisons to help include or exclude known fingerprints from further investigation. Subsequently, the analyst will examine specific points of a suspect print to corresponding points of a known fingerprint. If enough characteristics match up, the fingerprints are determined to be from the same person.

In every crime scene, a narrative lies behind every fingerprint, serving as the key to solving a heinous crime, or just an everyday occurrence. So, the next time you glance at your fingertips, remember the profound story they hold — the story of who you are and the imprint you leave on the world.

 

Citations:

Byrd, Mike. “Ridge Detail at a Crime Scene.” Crime Scene Investigator Network,

Accessed 28 Mar. 2024. 

P, Surat. “Fingerprint Analysis in Forensic Science.” AZoLifeSciences, 28 Oct. 2020,

Accessed 28 Mar. 2024. 

“Principles of Fingerprint Analysis.” Fingerprint Analysis: Principles, Forensic Science

Mar. 2024.

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