Probability Calculator for Paternity Likelihood Using STRs

Version 3.03e, Copyright(C) 2000-2015 Atsushi Akane-All rights reserved.
This web page calculates the probability of paternity likelihood using a JavaScript program.
Use Internet Explorer of the version more than 5.0.

The probability is obtained using allele frequencies of STRs in Japanese population
(Hashiyada M et al. Forensic Sci Int 133: 250-253, 2003).

  1. Select a type of polymorphic marker.

    For Y-STRs, only one marker should be selected for the calculation. Y-STRs compose a haplotype so that the total probability of paternity likelihood cannot be obtained by the product of likelihood ratios of all Y-STRs' markers.

  2. Select a polymorphic marker.
          Caution! Time-consuming!
    MEC (Mean
    Exclusion Chance)

    Probability of exclusion of non-father
    / HZ (Heterozygosity)
    Sum of frequencies of heterozygous genotypes
    / PE (Power of

    Probability of exclusion of non-father
    PD (Power of

    Chance of two persons being different genotypes
    / PIC (Polymorphic
    Information Contents)

    Probability of determining origins of child's alleles
    / TPI (Typical
    Paternity Index)

    Usefulness of a marker for disputed paternity testing
    PD (male)
    for X-STRs

    Chance of two men being different X-STR
    / PD (female)
    for X-STRs

    Chance of two women being different X-STR
    / MEC (II)
    for X-STRs

    Probability of exclusion of non-father using
    X-STRs in trios involving daughters

  3. Select two alleles each of mother, child and the alleged father (AF), and click the [calculate] button. The same allele must be selected twice in case of the homozygous genotype.
    When mother's genotype is not determined, select [n.d.]
    For X-STRs, the AF's second allele must be [Y]. The child must be a girl.
    For Y-STRs, two mother's alleles and the men's second alleles must be [X]. The child must be a boy.

    To input results of the next STR, go to Step #1 or Step #2.
    To see the total probability, go to Step #4.


    Frequency of AF's genotype (Y) X=H/K=
    Probability of mother-child
    combination (K)
    Probability of mother-child-
    AF combination (H)
    Likelihood ratio (X/Y)
    Probability of paternity likelihood (W)
    Probability of paternity exclusion (P)
    (Sum of frequencies of non-fathers' genotypes)

  4. Conclusion   Step #1   Step #2   Step #3
    Total likelihood ratio (X/Y)
    Total probability of paternity likelihood (W)     Conclusion
    Total probability of paternity exclusion (P)

  5. Records
        Select a polymorphic marker to be deleted from the left menu,
    and click the [Delete one] button.

    Return to menu