Basic Principles


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Richard Saferstein in his book Criminalistics describes the following fundamental principles of fingerprints;

1. A fingerprint is an individual characteristic

In the 90 years since fingerprinting was generally introduced, out of the millions of sets of prints that have been taken, no two individuals have been found to have the same fingerprints. 

It is not the shape of the print that is individual, but rather the number, location and shape of specific ridge characteristics (also known as minutiae). 

When comparing a print from a crime scene to a known print of a suspect the examiner is looking for minutiae in the same place on each print. This is complicated as it is rare to get a whole fingerprint at a crime scene so it is often  only a section of a print that is being compared. It is also common for the print to be distorted as it is pressed or rolled onto a surface, so that two prints from the same finger of the same person don't look the same.

The greater the number of matches of minutiae the smaller the probability of a mistake being made. Australian courts in a similar fashion to British courts require at least 16 minutiae to be matched before the fingerprint be used as evidence of identification.

Article from The Print*: A Review of the Sixteen Point Fingerprint Standard in England and Wales

*The official publication of the South California Association of Fingerprint Officers

2. A fingerprint will remain unchanged during an individual's lifetime

The ridges on the grasping surfaces of hands and on the soles of feet are present at birth and remain unchanged for life except for size as growth occurs. They may be obscured by deep tissue damage that causes scarring, like burns for example. However these scars may also be useful as points of identification.

3. Fingerprints have general ridge patterns that permit them to be systematically classified

Sir Francis Galton in his book Finger Prints (1892) classified fingerprint patterns into three main kinds;

Arches; 5 % population

Loops; 60 - 65 % 

Whorls; 30 - 35 %

  

This classification was extended by Sir Edward Henry in 1897 and it was this modified system that was adopted by Scotland Yard in 1901. This system of classification, with some variation, is still in use today in English speaking countries.

Classifying the general pattern of fingerprints allows them to be stored in a filing system and subsequently retrieved for comparison. Modern technology has allowed this process to transferred to computers with the advent of automated fingerprint identification systems (AFIS).

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Copyright 2000-2005  Deakin University, Comments to Author: Associate Professor Simon W. Lewis  Revised: June 13, 2005