Characterisation of artefacts and drop-in events using STR-validator and single-cell analysis

Hansson, Oskar; Gill, Peter

doi:10.1016/j.fsigen.2017.04.015

Cited by 26 publications

(20 citation statements)

References 46 publications

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“…The minute amount of a few cells or DNA molecules, which may be applicable for amplification, is not recognizable typically in an autopsy environment and is easily transferable between cases [4,117,118]. Although methodological developments are continuously making efforts to eliminate the effect of contamination artifacts from the profiling process [119,120], less appropriate autopsy sampling, incorporating the undetected contamination incidents, can lead to false interpretation within a DNA laboratory [5].…”

Section: Discussionmentioning

confidence: 99%

Most Common Medico-Legal Autopsy-Related Human and Nonhuman Biological Samples for DNA Analysis

Pádár¹,

Zenke²,

Kozma³

2018

Post Mortem Examination and Autopsy - Current Issues From Death to Laboratory Analysis

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The identification and individualization of biological evidences is crucial to actual criminal investigations. In spite of the differences at the national level, all the legal processes attribute particular importance to forensic DNA analysis. However, none of the qualified results from any professional laboratory can produce substantive, valuable evidence with insufficient quality of samples and/or problems with provision of a pristine and controlled environment. The methodology and efficiency of sampling are distinct in case of living persons and in medico-legal autopsy and crime scenes. This chapter is a short overview from the basic introductory information up to ongoing research, and in accordance with constraints on the chapter size, it briefly discusses the important topics of sample collection at medico-legal autopsy for DNA analysis. The content sorts the major types of samples, reviews the common methods of sampling and the potential risk of poor sampling or contamination transfer. The corpses can be more or less degraded, which in special cases (e.g., paraffin embedded tissues, drowned, burning and/or buried cadaver) allow only for analysis of highly degraded samples. The samples can be associated with tissues of a corpse (e.g., blood, soft tissues, bone, tooth, hair) and/or additional extraneous tissues and remains, which are often mixed (e.g., blood, saliva, semen, vaginal fluid, debris of fingernails) on the corpse.

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Section: Discussionmentioning

confidence: 99%

Most Common Medico-Legal Autopsy-Related Human and Nonhuman Biological Samples for DNA Analysis

Pádár¹,

Zenke²,

Kozma³

2018

Post Mortem Examination and Autopsy - Current Issues From Death to Laboratory Analysis

View full text Add to dashboard Cite

show abstract

“…We don’ t know how or why it is there [1]. Here background DNA is distinguished from drop-in [6, 7], defined as up to three alleles not observed in prevalent DNA. If four or more alleles are observed, then an ‘ unknown’ contributor is present and LR ϕ is calculated with eq: (2)…”

Section: Definitionsmentioning

confidence: 99%

AnLRframework incorporating sensitivity analysis to model multiple direct and secondary transfer events on skin surface

Gill

Bleka

Røseth

et al. 2021

Preprint

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Bayesian logistic regression is used to model the probability of DNA recovery following direct and secondary transfer and persistence over a 24 hour period between deposition and sample collection. Sub-source level likelihood ratios provided the raw data for activity-level analysis. Probabilities of secondary transfer are typically low, and there are challenges with small data-sets with low numbers of positive observations. However, the persistence of DNA over time can be modelled by a single logistic regression for both direct and secondary transfer, except that the time since deposition must be compensated by an offset value for the latter. This simplifies the analysis. Probabilities are used to inform an activity-level Bayesian Network that takes account of alternative propositions e.g. time of assault and time of social activities. The model is extended in order to take account of multiple contacts between person of interest and 'victim'. Variables taken into account include probabilities of direct and secondary transfer, along with background DNA from unknown individuals. The logistic regression analysis is Bayesian - for each analysis, 4000 separate simulations were carried out. Quantile estimates enable calculation of a plausible range of probabilities and sensitivity analysis is used to describe the corresponding variation of LRs that occur when modelled by the Bayesian network. It is noted that there is need for consistent experimental design, and analysis, to facilitate inter-laboratory comparisons. Appropriate recommendations are made. The open-source program written in R-code ALTRaP (Activity Level, Transfer, Recovery and Persistence) enables analysis of complex multiple transfer propositions that are commonplace in cases-work e.g. between those who cohabit. A number of case examples are provided. ALTRaP can be used to replicate the results and can easily be modified to incorporate different sets of data and variables.

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“…It is true that generating DNA profile from various low template containing DNA evidences helps in solving many forensic cases but It can be difficult to determine accurate DNA profile when working with low copy number template DNA. It has been observed that profile obtained from low quantity of template DNA contains allele drop-in or allele drop-out making it difficult to ascertain results and apply statistical calculations (Curran & Buckleton, 2010;Hansson & Gill, 2017). There is no consistent widespread methodology for allele designations in low template DNA-based profile, however, it has been suggested that repetitive methodologies can help increasing confidence level in DNA profile.…”

Section: Potential Risks Of Lcn Typing and Challengesmentioning

confidence: 99%

Generating DNA profile from low copy number DNA: Strategies and associated risks

Mateen¹,

Tariq

Hussain³

2020

Acta Sci. Biol. Sci.

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Many shreds of evidence found on the crime scenes contain a trace amount of DNA which results in insignificant profiling results for subsequent comparison. This can nullify the potential evidence material and hamper investigation process. Over the years, different strategies have been employed by various DNA testing laboratories to create interpretable DNA profiles generated from low template of DNA. This review highlights different strategies used by forensic laboratories worldwide for creating complete DNA profiles from low copy number template for comparison purposes along with its associated risks for forensic purposes

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Characterisation of artefacts and drop-in events using STR-validator and single-cell analysis

Cited by 26 publications

References 46 publications

Most Common Medico-Legal Autopsy-Related Human and Nonhuman Biological Samples for DNA Analysis

Most Common Medico-Legal Autopsy-Related Human and Nonhuman Biological Samples for DNA Analysis

AnLRframework incorporating sensitivity analysis to model multiple direct and secondary transfer events on skin surface

Generating DNA profile from low copy number DNA: Strategies and associated risks

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