Likelihood ratio statistics for DNA mixtures allowing for drop-out and drop-in

Mitchell, Adele A.; Tamariz, Jeannie; O’Connell, Kathleen; Ducasse, Nubia; Prinz, Mechthild; Caragine, Theresa

doi:10.1016/j.fsigss.2011.08.119

Cited by 7 publications

(5 citation statements)

References 4 publications

(4 reference statements)

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“…While RMPs were generated to demonstrate the potential utility of nuclear DNA assays when compared to mtDNA sequencing, more complex interpretation models utilizing likelihood ratios can include probabilities for allele drop‐in and dropout. This would only be possible with appropriate validations with the assays in questions [27].…”

Section: Methodsmentioning

confidence: 99%

Novel extraction chemistry and alternative amplification strategies for use with rootless hair shafts

Gutierrez

LaRue²,

Houston

2021

Journal of Forensic Sciences

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Rootless hair shafts are often considered unsuitable for STR genotyping due to the known high failure rate. The same samples can be reliably processed with mitochondrial sequencing. However, the minimal discriminatory power of widely implemented control region mitochondrial sequencing techniques limits its utility in some forensic casework. In this research, multiple variables were tested to provide information on rootless hair shaft sample genotyping success. Results showed external decontamination procedures decreased drop-in alleles but also greatly reduced profile recovery. The novel InnoXtract ™ chemistry was comparable to automated EZ1 DNA Investigator extraction. With thoroughly decontaminated hairs, InnoTyper ® 21 amplification generated random match probabilities higher than STR chemistry in 71.875% of samples and 18.75% of samples benefitted from the use of InnoTyper ® 21 amplification compared with estimated mtDNA profile rarity. Compared with the capillary electrophoresis-based amplification chemistries tested, the ForenSeq™ DNA Signature Prep chemistry paired with massively parallel sequencing was the most discriminatory amplification strategy tested.

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Section: Methodsmentioning

confidence: 99%

Novel extraction chemistry and alternative amplification strategies for use with rootless hair shafts

Gutierrez

LaRue²,

Houston

2021

Journal of Forensic Sciences

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“…The probabilistic interpretation of DNA evidences recovered on crime scenes has been for many years a largely debated and investigated issue in the field of forensic biology [1][2][3][4][5][6][7][8], especially in case of Low-Template DNA (LT-DNA) samples. There are several questions and multiple choices, indeed, that the analysts have to face when bio-statistical interpretation processes on DNA mixtures take place, such as: (i) the calculation of analytical and stochastic thresholds [9][10][11], (ii) the evaluation of the most probable number of contributors composing the DNA samples [12][13][14][15][16][17], (iii) the establishment of parameters such as drop-in rate, drop-out rate [6,9,[18][19][20][21][22][23], stutters rate [24,25] and co-ancestry coefficient (F st ) [26,27], (iv) the selection of the appropriate allele frequency dataset [28]. Moreover, the use of the appropriate model to be adopted on the acquired data to perform bio-statistical interpretations is essentialbio-statistical interpretation, with the most accurate model, is essential.…”

Section: Introductionmentioning

confidence: 99%

DNA mixtures interpretation – A proof-of-concept multi-software comparison highlighting different probabilistic methods’ performances on challenging samples

Alladio

Omedei

Cisana

et al. 2018

Forensic Science International: Genetics

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The present study investigated the capabilities and performances of semi-continuous and fully-continuous probabilistic approaches to DNA mixtures interpretation, particularly when dealing with Low-Template DNA mixtures. Five statistical interpretation software, such as Lab Retriever and LRmix Studio - involving semi-continuous algorithms - and DNA•VIEW, EuroForMix and STRmix- employing fully-continuous formulae - were employed to calculate likelihood ratio, comparing the prosecution and the defense hypotheses relative to a series of on-purpose prepared DNA mixtures that respectively contained 2 and 3 known contributors. National Institute of Standards and Technologies (NIST) certified templates were used for samples set up, which contained different DNA amounts for each contributor. 2-person mixtures have been prepared with proportions equal to 1:1, 19:1 and 1:19 in terms of DNA concentration. Conversely, three person mixtures were constituted by proportions equal to 20:9:1, 8:1:1, 6:3:1 and 1:1:1 in terms of DNA concentration. Furthermore, 8 equally-proportioned 3-person mixtures were prepared by means of scalar dilutions starting from an overall amount of 0.500 ng, then ranging up to DNA samples with concentrations equal to 0.004 ng (i.e. Low-Template DNA). DNA mixtures were set up in triplicate and amplified with 7 DNA amplification kits (i.e. GlobalFiler PCR Amplification Kit, NGM SElect PCR Amplification Kit, MiniFiler PCR Amplification Kit, Power Plex Fusion, PowerPlex 6C Matrix System, Power Plex ESI 17 Fast and Power Plex ESX 17 Fast) in order to evaluate whether the selection of a certain kit might represent a bias factor, capable of altering the whole interpretation process. A multi-software approach helped us to highlight any trend in the likelihood ratio results provided by semi- and fully-continuous software. As a matter of fact, fully-continuous computations provided different (higher) results in terms of degrees of magnitude of the likelihood ratio values with respect to those from the semi-continuous approach, regardless of the amplification kit that was utilized.

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“…The International Society for Forensic Genetics (ISFG) DNA commission [1] recognized likelihood ratios (LRs) to be the preferred way to associate strength of evidence of DNA mixtures. Since then a number of different methods have been described [2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Euroforgen-NoE collaborative exercise on LRmix to demonstrate standardization of the interpretation of complex DNA profiles

Prieto¹,

Haned

Mosquera

et al. 2014

Forensic Science International: Genetics

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There has been very little work published on the variation of reporting practices of mixtures between laboratories, but it has been previously demonstrated that there is little consistency. This is because there is no current uniformity of practice, so different laboratories will operate using different rules. The interpretation of mixtures is not solely a matter of using some software to provide 'an answer'. An assessment of a case will usually begin with a consideration of the circumstances of a crime. Assumptions made about the numbers of contributors follow from an examination of the electropherogram(s)--and these may differ between the prosecution and the defence hypotheses. There may be a necessity to evaluate several sets of hypotheses for any given case if the circumstances are uncertain. Once the hypotheses are formulated, the mathematical analysis is complex and can only be accomplished by the use of specialist software. In order to obtain meaningful results, it is essential that scientists are trained, not only in the use of the software, but also in the methodology to understand the likelihood ratio concept that is used. The Euroforgen-NoE initiative has developed a training course that utilizes the LRmix program to carry out the calculations. This software encompasses the recommendations of the ISFG DNA commissions on mixture interpretation and is able to interpret samples that may come from two or more contributors and may also be partial profiles. Recently, eighteen different laboratories were trained in the methodology. Afterwards they were asked to independently analyze two different cases with partial mixture DNA evidence and to write a statement court-report. We show that by introducing a structured training programme, it is possible to demonstrate, for the first time, that a high degree of standardization, leading to uniformity of results can be achieved by participating laboratories.

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Likelihood ratio statistics for DNA mixtures allowing for drop-out and drop-in

Cited by 7 publications

References 4 publications

Novel extraction chemistry and alternative amplification strategies for use with rootless hair shafts

Novel extraction chemistry and alternative amplification strategies for use with rootless hair shafts

DNA mixtures interpretation – A proof-of-concept multi-software comparison highlighting different probabilistic methods’ performances on challenging samples

Euroforgen-NoE collaborative exercise on LRmix to demonstrate standardization of the interpretation of complex DNA profiles

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