Impact Of Relatives On Str Profile Frequency Estimates

If the suspect and the true perpetrator of a crime are related, then their genotype frequencies are not independent and a different calculation is required (Weir 1994, Weir 2003). Since STR profiles from relatives are expected to be more similar to the individual in question than a random, unrelated individual, NRC II recommendation 4.4 covers probability calculations from various scenarios of individuals related to the suspect. Table 21.6 works through the same DNA profile according to NRC II recommendations 4.4 and equations 4.8a and 4.8b (see Appendix VI).

More recently, Weir (2003) has developed match probability formulas to calculate the effects of family relatedness that incorporate population substructure functions into them. These formula are listed in Table 21.7 along with a worked example using a homozygote TH01 6,6 Caucasian allele frequency and a heterozygote D13S317 11,14 Caucasian allele frequencies. Note that in the case of the TH01 6,6 example the match probability increases from 0.06283 for an unrelated individual to 0.38921 for full siblings - an increase of more than sixfold. Likewise, the random match probability of the heterozygote D13S317

II,14 changes 9.3-fold from 0.03864 to 0.35955 when moving from an unrelated individual to a full sibling.

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Stammering Its Cause and Its Cure

Stammering Its Cause and Its Cure

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