Likelihood ratio formulae for disputed parentage when the product of conception is trisomic

Duncan A. Taylor, Oliva Handt, Damien Abarno, John Buckleton

Research output: Contribution to journalArticlepeer-review


We present here the derivation of paternity index formulae that covers situations of a disputed paternity trio with a trisomic product of conception. We consider six possible mechanisms for trisomy to occur: dispermy, dieggy, paternal meiosis I or II, and maternal meiosis I or II in the calculation. We also provide a biological explanation for how each of the mechanisms could give rise to a trisomy. The paper is set out in a general manner so that the tables presented can be used on any instance of trisomic offspring. This work is motivated by a case of disputed paternity where the product of conception was trisomic, i.e. the electropherogram of the product of conception possessed three alleles at each locus. The outcome was extremely strong support for the alleged father’s paternity of the product of conception.

Original languageEnglish
Pages (from-to)1513-1521
Number of pages9
JournalInternational Journal of Legal Medicine
Issue number6
Publication statusPublished - 1 Nov 2017


  • Formulae look-up table
  • Likelihood ratio
  • Paternity index
  • Triploidy
  • Trisomic


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