The low-template-DNA (stochastic) threshold - Its determination relative to risk analysis for national DNA databases

P. Gill, R. Puch-Solis, James Curran

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67 Citations (Scopus)


Although the low-template or stochastic threshold is in widespread use and is typically set to 150-200 rfu peak height, there has been no consideration on its determination and meaning. In this paper we propose a definition that is based upon the specific risk of wrongful designation of a heterozygous genotype as a homozygote which could lead to a false exclusion. Conversely, it is possible that a homozygote fa,a) could be designated as {a,F} where 'F is a 'wild card', and this could lead to increased risk of false inclusion. To determine these risk levels, we analysed an experimental dataset that exhibited extreme drop-out using logistic regression. The derived probabilities are employed in a graphical model to determine the relative risks of wrongful designations that may cause false inclusions and exclusions. The methods described in this paper provide a preliminary solution of risk evaluation for any DNA process that employs a stochastic threshold.
Original languageEnglish
Pages (from-to)104-111
Number of pages7
JournalForensic Science International: Genetics
Issue number2
Publication statusPublished - Mar 2009


  • STR
  • extreme drop-out
  • low-level-DNA (stochastic) threshold
  • national DNA database
  • low-copy-number

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