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Masthead - Forensic Science Communications
July 2000   Volume 2   Number 3

Source Attribution of a
Forensic DNA Profile

Table 1

Random Match Probability Thresholds for Source Attribution at Various Population Sizes and Confidence Levels

Sample Size (N)

Confidence Levels
0.90 0.95 0.99 0.999
2 5.1 × 10-2 2.5 × 10-2 5.0 × 10-3 5.0 × 10-4
3 3.5 × 10-2 1.7 × 10-2 3.3 × 10-3 3.3 × 10-4
4 2.6 × 10-2 1.3 × 10-2 2.5 × 10-3 2.5 × 10-4
5 2.1 × 10-2 1.0 × 10-2 2.0 × 10-3 2.0 × 10-4
6 1.7 × 10-2 8.5 × 10-3 1.7 × 10-3 1.7 × 10-4
7 1.5 × 10-2 7.3 × 10-3 1.4 × 10-3 1.4 × 10-4
8 1.3 × 10-2 6.4 × 10-3 1.3 × 10-3 1.3 × 10-4
9 1.2 × 10-2 5.7 × 10-3 1.1 × 10-3 1.1 × 10-4
10 1.1 × 10-2 5.1 × 10-3 1.0 × 10-3 1.0 × 10-4
25 4.2 × 10-3 2.1 × 10-3 4.0 × 10-4 4.0 × 10-5
50 2.1 × 10-3 1.0 × 10-3 2.0 × 10-4 2.0 × 10-5
100 1.1 × 10-3 5.1 × 10-4 1.0 × 10-4 1.0 × 10-5
1 × 103 1.1 × 10-4 5.1 × 10-5 1.0 × 10-5 1.0 × 10-6
1 × 105 1.1 × 10-6 5.1 × 10-7 1.0 × 10-7 1.0 × 10-8
1 × 106 1.1 × 10-7 5.1 × 10-8 1.0 × 10-8 1.0 × 10-9
1 × 107 1.1 × 10-8 5.1 × 10-9 1.0 × 10-9 1.0 × 10-10
5 × 107 2.1 × 10-9 1.0 × 10-9 2.0 × 10-10 2.0 × 10-11
2.6 × 108 4.1 × 10-10 2.0 × 10-10 3.9 × 10-11 3.9 × 10-12
1 × 109 1.1 × 10-10 5.1 × 10-11 1.0 × 10-11 1.0 × 10-12
5 × 109 2.1 × 10-11 1.0 × 10-11 2.0 × 10-12 2.0 × 10-13

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FORENSIC SCIENCE COMMUNICATIONS     JULY 2000   VOLUME 2   NUMBER 3

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