Interpreting DNA mixtures.

  title={Interpreting DNA mixtures.},
  author={Bruce S. Weir and Christopher M. Triggs and L Starling and L I Stowell and Kevan A. J. Walsh and John S. Buckleton},
  journal={Journal of forensic sciences},
  volume={42 2},
The interpretation of mixed DNA stains is explained in the context of likelihood ratios. The probabilities for the mixed-stain profile are evaluated under alternative explanations that specify the numbers of contributors and the profiles of any known contributors. Interpretations based simply on the frequencies with which random members of a population would not be excluded from a mixed-stain profile do not make use of all the information, and may overstate the strength of the evidence against… 

Tables from this paper

Interpreting DNA mixtures with the presence of relatives
The kinship coefficients are incorporated into the evaluation of the likelihood ratio and a unified expression of joint genotypic probabilities is derived that can be applied to the case of a non-tested suspect with one tested relative.
Confidence Interval of the Likelihood Ratio Associated with Mixed Stain DNA Evidence *
This work proposes the use of a confidence interval to report the consequent variation of likelihood ratios, and shows that the evidential strength of DNA profiles decreases as the variation among populations increases.
Mixture Interpretation: DNA
DNA mixtures represent an increasing fraction of forensic DNA casework. They are currently interpreted by one of at least three methods. These are extract from the mixed DNA profile, when
Interpreting DNA mixtures in structured populations.
DNA profiles from multiple-contributor samples are interpreted by comparing the probabilities of the profiles under alternative propositions, and membership of the same subpopulation implies a relationship from a shared evolutionary history, and this effect has been incorporated into the probabilities.
Evaluation of DNA Mixtures Accounting for Sampling Variability
Within a Bayesian framework, the evaluation of DNA mixtures accounting for sampling variability in the population database of allele frequencies are discussed and the resulting formulae are shown to be more conservative, which is generally more favorable to the defendant.
Interpreting forensic DNA mixtures: allowing for uncertainty in population substructure and dependence
A general formula for calculating the match probabilities of DNA profiles is developed, which is often more to the benefit of the defendant in comparison with the simple product rule result based on an independence assumption.
Estimating the number of contributors to a DNA profile
This paper addresses DNA mixtures based on single nucleotide polymorphism (SNP) markers, i.e., diallelic markers, by first approaching the more general problem of estimating the number of contributors to a stain and how the markers should be selected and how many are required.
DNA mixtures: biostatistics for mixed stains with haplotypic genetic markers
A novel theory which accounts for the features of haplotypic markers has been developed within the general framework of the hypotheses testing approach and opens the way for the use of haplotypesic markers in the analysis of mixed stains with the arbitrary numbers of unknown contributors and linked loci.
The interpretation of low level DNA mixtures.


Nondetectability of restriction fragments and independence of DNA fragment sizes within and between loci in RFLP typing of DNA.
Using a known statistical method, an efficient estimate of null allele frequency is derived, which may be subsequently used for testing allelic independence within and across loci, and is shown to agree with direct experimental data on the frequencies of HaeIII-null alleles.
Forensic application of DNA ‘fingerprints’
It is shown that this technique can be used for forensic purposes; DNA of high relative molecular mass (Mr) can be isolated from 4-yr-old bloodstains and semen stains made on cotton cloth and digested to produce DNA fingerprints suitable for individual identification.
What is the probability that this blood came from that person? A meaningful question?
  • I. Evett
  • Sociology
    Journal - Forensic Science Society
  • 1983
Nondetectability of restriction fragment sizes within and between loci in RFLP typing of DNA
  • Am J Human Genet
  • 1994
Interpreting DNA mixtures Additional information and reprint requests
  • J Forensic Sci
  • 1997
The effects of inbreeding on forensic calculations.
  • B. Weir
  • Biology, Medicine
    Annual review of genetics
  • 1994
DNA technology in forensic science
  • DNA technology in forensic science
  • 1992