Table of contentsHaplotype DNA evidence
Analysis of Y-haplotype information in a kinship case
Forensic mathematics home page
Comments are welcome (see home page for email)
The strength of the evidence is therefore simply expressed as matching odds (or equivalently as a likelihood ratio) of
matching odds = 1 / P(haplotype).
PI = 1 / P(haplotype).
Suppose a man M has Y-haplotype which we call
Obviously, mutation cannot be ignored in this case. Since
There are several possible approaches. We use the notation PI for the
paternity index, and
PI = X/Y, where
X = Prob(observed haplotypes | F father C) and
Y = Prob(observed haplotypes | F unrelated to C).
To evaluate Y, we can write
X is a little more problematic.
LR = X/Y = X/
It remains to estimate
Note that all formulas are equivalent if
|Hence LR = 30.009/2(2/171) = 1.15.|
The meaning of this neutral result is that the chance to see so rare a haplotype by mutation is about the same as the chance to see it at random in an unrelated individual.
My recent paper on rare haplotypes offers several approaches. Bottom line: simple counting (but add 1) is very conservative. A pretty accurate method that is not complicated is also given. June 2009