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Example 4 is for illustration only. The numbers used in the example are hypothetical.
The goal of the example is to illustrate that a 6-point match between two fingerprints is not sufficient to conclude that the fingerprints came from the same person.
There is no agreement on how many points need to match to conclude that two fingerprints come from the same individual. According to the National Institute of Standards and Technology, a latent fingerprint will usually have at least 12 minutiae points in common with a file fingerprint. Complete fingerprints will usually match on at least 50 minutiae points.
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Fingerprinting was first used by the ancient Babylonians to record business transactions. The ancient Chinese also used it for business and identifying children. Using fingerprints to identify criminals began in the late 19th century and was first used as court evidence in 1902. The FBI's Identification Division maintains the Integrated Automated Fingerprint Identification System. The IAFIS contains criminal histories and fingerprints for more than 70 million subjects in the criminal file, including 73,000 known or suspected terrorists worldwide.
For more information about the collection and matching of fingerprints, visit the National Institute of Standards and Technology.
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You can continue the pattern in Example 4 as follows.
1 billion people have Point 1
20 % of these also have Point 2
20 % of these also have Point 3
20 % of these also have Point 4
20 % of these also have Point 5
20 % of these also have Point 6
20 % of these also have Point 7
20 % of these also have Point 8
20 % of these also have Point 9
20 % of these also have Point 10
20 % of these also have Point 11
20 % of these also have Point 12
1,000,000,000 people
200,000,000 people
40,000,000 people
8,000,000 people
1,600,000 people
320,000 people
64,000 people
12,800 people
2,560 people
512 people
102 people
20 people
1-point match
2-point match
3-point match
4-point match
5-point match
6-point match
7-point match
8-point match
9-point match
10-point match
11-point match
12-point match
So, using the hypothesis that any two people have a 20% likelihood of matching one and two fingerprint points, there are up to 20 people out of a billion that have a 12-point match.
If you continue this pattern for 16 points, you will see there is an even greater likelihood the two fingerprints "absolutely" came from the same person.
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Ron Larson (author)1 decade ago |When I was writing this book, there were many times when my mind would wander and think about happy or sad things that have happened to people. When I was researching and writing this example, I thought about the tragic miscarriages of justice in which innocent people have been convicted of crimes in which the condemning evidence was a fingerprint "match" based on too few points.1 0