Applying calibration to <i>LR</i>s produced by a DNA interpretation software

Bright, Jo‐Anne; Dukes, M.J.M.; Pugh, Simone N.; Evett, I.W.; Buckleton, John

doi:10.1080/00450618.2019.1682668

Cited by 11 publications

(16 citation statements)

References 19 publications

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“…Calibration tests that LRs of any given magnitude are occurring at the expected rate. It has been applied to STRmix™ and EuroForMix [57,58].…”

Section: Non-contributor Tests and Calibration Of The Lrmentioning

confidence: 99%

“…Reference Ability of STRmix™ to deconvolute profiles and assign LRs that comport to manual interpretation and human expectation [15] Ability of STRmix™ to discriminate between donors and non-donors in database searches [190] Behaviour of STRmix™ to assign LRs when dealing with multiple replicates, different number of contributors, and assumed contributors [163] Sensitivity of LR produced by STRmix™ to different factors of uncertainty such as theta, relatedness of alternate DNA source and length of MCMC analysis [171] Tests to be performed when validating probabilistic genotyping, using STRmix™ as an example [112] Ability of individuals from different laboratories to standardise evaluations when using STRmix™ [33,53] Ability of STRmix™ to reliably use peak height information in very low intensity profiles [56,132,210] Ability of STRmix™ to discriminate between donors and non-donors in large-scale Hd true tests, or using importance sampling [59,60,190,200,21 2,213] Sensitivity of STRmix™ model parameters to laboratory factors [196,198] Ability of STRmix™ to utilise information from profiles produced under different laboratory conditions within a single analysis [155] Effect of mixture complexity, allele sharing and contributor proportions on the ability STRmix™ to distinguish contributors from non-contributors [54] The ability of STRmix™ to identify common DNA donors in mixed samples [25,159] The sensitivity of LRs produced in STRmix™ to the choice of the number of contributors [71,72,97] Ability to use STRmix™ to resolve major components of mixtures [72] Testing the assumption of additivity of peak heights in STRmix™ models [159,160] Performance of the degradation model within STRmix™ [214] The effect of relatedness of contributors to the STRmix™ analysis [203,215] Testing the calibration of LRs produced in STRmix™ [58] Validation overviews of STRmix™ [205,216] Comparison of STRmix™ ...…”

Section: Focus Of Validationmentioning

confidence: 99%

See 1 more Smart Citation

A Review of Probabilistic Genotyping Systems: EuroForMix, DNAStatistX and STRmix™

Gill

Benschop

Buckleton

et al. 2021

Genes

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Probabilistic genotyping has become widespread. EuroForMix and DNAStatistX are both based upon maximum likelihood estimation using a γ model, whereas STRmix™ is a Bayesian approach that specifies prior distributions on the unknown model parameters. A general overview is provided of the historical development of probabilistic genotyping. Some general principles of interpretation are described, including: the application to investigative vs. evaluative reporting; detection of contamination events; inter and intra laboratory studies; numbers of contributors; proposition setting and validation of software and its performance. This is followed by details of the evolution, utility, practice and adoption of the software discussed.

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“…Calibration tests that LRs of any given magnitude are occurring at the expected rate. It has been applied to STRmix™ and EuroForMix [57,58].…”

Section: Non-contributor Tests and Calibration Of The Lrmentioning

confidence: 99%

Section: Focus Of Validationmentioning

confidence: 99%

A Review of Probabilistic Genotyping Systems: EuroForMix, DNAStatistX and STRmix™

Gill

Benschop

Buckleton

et al. 2021

Genes

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“…Nor do they argue with my suggestion that forensic scientists need to consider carefully whether to report results in such cases and perhaps develop standards to address that issue. The research they cite on calibration [5,6] convinces me that the LRs produced by STRMix are reasonably well calibrated in most cases, but the calibration research is all based on analysis of mixtures "made to target a total DNA of 500 pg" [5]. Whether calibration will be as good in cases like the one discussed here where the total amount of DNA was <100 pg has not been established.…”

Section: Deficient Validationmentioning

confidence: 93%

Author's response

Thompson

2023

Journal of Forensic Sciences

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See Original Article here See Commentary on here Editor, When I learned that two programs for probabilistic genotyping had produced widely different results for the same case, I wanted to understand how that could have happened. My article [1] about the case was a first cut at explaining an event that I found extraordinary. In their comment, Buckleton et al. [2] suggest that there is really nothing surprising about what I observed. By their account, the two programs are similar and produce different outputs only because they received different inputs due to differing analytic thresholds. To the forensic science community, they seem to be saying: "move along folks, there is nothing to see here." They appear to agree with some of my points about reporting PG results, but they suggest that the attention I devoted to comparing the performance of STRMix and TrueAllele in this case "was not warranted" [2].Yet there is far more going on here than "different inputs producing different outputs." It is worth repeating that the two programs were analyzing the same case using the same data file. While the analytic thresholds the analysts chose to apply were different, there is no way to know which threshold was more appropriate, and hence no way of knowing which of the widely different result is more trustworthy. The suggestion that the programs actually led to the same "interpretation" because both produced exculpatory results is unconvincing when the likelihood ratios (LRs) supporting that interpretation differed by five to six orders of magnitude. While DNA evidence ultimately played a minor role in the case that I discussed, DNA evidence of a similar type-based on "very low information content profiles"-is playing an increasingly important role in the legal system. Hence, the conflicting results and approaches to analysis and reporting that occurred in this case will certainly re-occur in other cases. Indeed, in a non-peer-reviewed online posting, Mark Perlin and his employees assert that "Cybergenetics has re-analyzed STRMix 'inconclusive' or weak LR results on 85 evidence items, finding stronger exclusionary results for 55 of them (65%)" [3]. While Perlin et al. [3] make a number of false assertions in the same online posting [4], their comments make it clear that the case I highlighted is not the only one in which the two PG systems have produced differing results. In my view, such differences warrant careful consideration by the scientific and legal communities.

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“…However, to be useful this knowledge needs to be transformed into which, if any, of the software is credible and if so under what conditions. This is best undertaken by calibration [4] (see [5,6] for some STRmix™ calibrations). We do commend Thompson's locus by locus examination and the scoring against his subjective expectations.…”

Section: Ifferent a N S Wer S From D Ifferent Sof T Warementioning

confidence: 99%

Commentary on: Thompson WC. Uncertainty in probabilistic genotyping of low template DNA: a case study comparing STRmix™ and TrueAllele™. J Forensic Sci. 2023;68 (3):1049–63. doi: 10.1111/1556‐4029.15225

Kalafut,

Curran,

Coble

et al. 2023

Journal of Forensic Sciences

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Applying calibration to LRs produced by a DNA interpretation software

Cited by 11 publications

References 19 publications

A Review of Probabilistic Genotyping Systems: EuroForMix, DNAStatistX and STRmix™

A Review of Probabilistic Genotyping Systems: EuroForMix, DNAStatistX and STRmix™

Author's response

Commentary on: Thompson WC. Uncertainty in probabilistic genotyping of low template DNA: a case study comparing STRmix™ and TrueAllele™. J Forensic Sci. 2023;68 (3):1049–63. doi: 10.1111/1556‐4029.15225

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