Using the Nondonor Distribution to Improve Communication and Inform Decision Making for Low LRs from Minor Contributors in Mixed DNA Profiles

Schuerman, Curt; Kalafut, Tim; Buchanan, Clint; Sutton, Joel; Bright, Jo‐Anne

doi:10.1111/1556-4029.14306

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…Conditioning has previously been shown to be highly valuable for all mixtures, especially those with high allelic overlap [5,7,10,11] such as mixtures of close relatives.…”

Section: We Use Different Sets Of Propositions Which Lead To Differentmentioning

confidence: 99%

A mixed DNA profile controversy revisited

Kalafut

Pugh²,

Gill

et al. 2021

Journal of Forensic Sciences

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Semaan et al. (J Forensic Res, 2020, 11, 453) discuss a mock case “where eight different individuals [P1 through P8] could not be excluded in a mixed DNA analysis. Even though … expert DNA mixture analysis software was used.” Two of these are the true donors. The LRs reported are incorrect due to the incorrect entry of propositions into LRmix Studio. This forced the software to account for most of the alleles as drop‐in, resulting in LRs 60–70 orders of magnitude larger than expected. P1, P2, P4, P5, and P8 can be manually excluded using peak heights. This has relevance when using LRmix which does not use peak heights. We extend the work using the same two reference genotypes who were the true contributors as Semaan et al. (J Forensic Res, 2020, 11, 453). We simulate three two‐donor mixtures with peak heights using these two genotypes and analyze using STRmix™. For the simulated 1:1 mixture, one of the non‐donors’ LRs supported him being a contributor when no conditioning was used. When considered in combination with any other potential donors (i.e., with conditioning), this non‐donor was correctly eliminated. For the 3:1 mixture, all results correctly supported that the non‐donors were not contributors. The low‐template 4:1 mixture LRs with no conditioning showed support for all eight profiles as donors. However, the results from pair‐wise conditioning showed that only the two ground truth donors had LRs supporting that they were contributors to the mixture. We recommend the use of peak heights and conditioning profiles, as this allows better sensitivity and specificity even when the persons share many alleles.

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“…Conditioning has previously been shown to be highly valuable for all mixtures, especially those with high allelic overlap [5,7,10,11] such as mixtures of close relatives.…”

Section: We Use Different Sets Of Propositions Which Lead To Differentmentioning

confidence: 99%

A mixed DNA profile controversy revisited

Kalafut

Pugh²,

Gill

et al. 2021

Journal of Forensic Sciences

Self Cite

View full text Add to dashboard Cite

show abstract

“…Another article mentions allele sharing, pointing out a neutral approach to sample selection: "No attempt was made to maximize or minimize the amount of allele sharing between donors" (Schuerman et al 2020).…”

Section: Degree Of Allele Sharingmentioning

confidence: 99%

(Draft) DNA Mixture Interpretation

Butler¹

2021

Preprint

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The initial release of this report is a draft document, and we welcome comments and feedback from readers. All relevant submitted comments will be made publicly available and will be considered when finalizing this report. Do not include personal information, such as account numbers or Social Security numbers, or names of other individuals. Do not submit confidential business information, or otherwise proprietary, sensitive, or protected information. We will not post or consider comments that contain profanity, vulgarity, threats, or other inappropriate language or like content. During the 60-day comment period, comments may be sent to scientificfoundationreviews@nist.gov. All comments, including commenter name and affiliation, will be published at https://www.nist.gov/dna-mixture-interpretation-nist-scientific-foundation-review. Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the authors or the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.

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“…For low positive log10LRs, it is important that a similar warning is given. One way to provide this understanding is with a graphical display of the distribution of the LR under the assumption that the alternative proposition, Ha, is true, along with the value for the LR in the case [9]. The existence of positive log10LRs from non-donors should not be a surprise to any scientist 1 ; indeed, with the frequentist approach, this observation was captured in the high probability values given in casework.…”

Section: Introductionmentioning

confidence: 99%

Are low LRs reliable?

Buckleton

Pugh²,

Bright

et al. 2020

Forensic Science International: Genetics

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To answer the question "Are low likelihood ratios reliable?" requires both a definition of reliable and then a test of whether low likelihood ratios (LRs) meet that definition. We offer, from a purely statistical standpoint, that reliability can be determined by assessing whether the rate of inclusionary support for non-donors is not larger than expected from the LR value. Thus, it is not the magnitude of the LR alone that determines reliability. Turing's rule is used to inform the expected rate of non-donor exclusionary support, where the rate of non-donor inclusionary support is at most the reciprocal of the LR, i.e. Pr(LR > x | Ha) < 1/x.There are parallel concerns about whether the value of the evidence can be communicated. We do not discuss that in depth here although it is an important consideration to be addressed with training.In this paper, we use a mixture of real and simulated data to show that the rate of non-donor inclusionary support is significantly lower than the upper bound given by Turing's rule. We take this as strong evidence that low LRs are reliable.

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Using the Nondonor Distribution to Improve Communication and Inform Decision Making for Low LRs from Minor Contributors in Mixed DNA Profiles

Cited by 6 publications

References 29 publications

A mixed DNA profile controversy revisited

A mixed DNA profile controversy revisited

(Draft) DNA Mixture Interpretation

Are low LRs reliable?

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