Publications by authors named "Kristy Steensma"

6 Publications

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Erratum to "DNA detection of a temporary and original user of an office space" [Forensic Sci. Int. Genet. (2020) 102203].

Forensic Sci Int Genet 2020 Jul 31;47:102277. Epub 2020 Mar 31.

Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, Australia; School of Molecular Sciences, College of Science, Health and Engineering, La Trobe University, Bundoora, Australia.

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http://dx.doi.org/10.1016/j.fsigen.2020.102277DOI Listing
July 2020

DNA transfer to worn upper garments during different activities and contacts: An inter-laboratory study.

Forensic Sci Int Genet 2020 05 4;46:102268. Epub 2020 Mar 4.

Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, Australia; School of Molecular Sciences, La Trobe University, Bundoora, Australia.

Cellular material derived from contact traces can be transferred via many direct and indirect routes, with the manner of contact and the time of transfer (in relation to the alleged crime-event) having an impact on whether DNA is recovered from the surface and a reportable profile generated. In an effort to acquire information on the transfer and recovery of DNA traces from clothing items worn during scenarios commonly encountered in casework, upper garments were worn during a normal working day before individuals were paired to embrace one another ('contact'), go on an outing together ('close proximity'), or individually asked to spend a day in another person's environment ('physical absence'). Each prescribed activity was repeated by sixteen individuals across four countries, and was the last activity performed before the garment was removed. Samples were collected from several areas of the upper garments and processed from DNA extraction through to profiling within the laboratory of the country in which the individual resided. Activities relating to the garment prior to and during wearing, including the prescribed activity, were recorded by the participant and considered during the interpretation of results. In addition to obtaining reference profiles from the wearer and their activity partner, DNA profiles from the wearers' close associates identified in the questionnaire were obtained to assess the impact of background DNA transferred prior to the prescribed activity. The wearer was typically, but not always, observed as the major contributor to the profiles obtained. DNA from the activity partner was observed on several areas of the garment following the embrace and after temporarily occupying another person's space. Particular areas of the garment were more prone to acquiring the hugging partner or office owner's DNA than others, and whether they were observed as the major or minor component was activity dependent. For each of the pairs, no DNA from the activity partner was acquired by the garments during the outing, even though both participants were in close proximity. This study provides empirical data on the transfer, persistence, prevalence and recovery of DNA from clothing items, and enables a better understanding of the mechanisms which lead to the transfer and detectability of DNA traces in different scenarios.
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http://dx.doi.org/10.1016/j.fsigen.2020.102268DOI Listing
May 2020

DNA detection of a temporary and original user of an office space.

Forensic Sci Int Genet 2020 01 11;44:102203. Epub 2019 Nov 11.

Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, Australia; School of Molecular Sciences, College of Science, Health and Engineering, La Trobe University, Bundoora, Australia.

There is a need to improve our awareness of the transfer, persistence, prevalence and recovery of DNA (DNA-TPPR) from items/surfaces, and within different spaces and circumstances, to assist sample targeting during collection and activity level assessments. Here we investigate DNA-TPPR within office spaces. Specifically, to what extent DNA, left by a temporary user of an office space that has been occupied by a regular user for an extended period, is detectable when the duration of their temporary occupancy and their general activities are known. Also, how readily the DNA of the regular user is still detectable after a known period of occupancy by another person, and to what extent DNA of others is present. Samples were collected from 18 core items/surfaces within eight single use office spaces that had been used temporarily by another occupant for 2.5-7 h. Four of these offices were within one forensic laboratory and four within another. Each lab collected and processed the samples to generate DNA profiles using their own set of methodologies. The owner/regular user of an office space was found to be the major/majority contributor to profiles from most items within the space, even after temporary use by another person. The detectability of the temporary occupier of an office space varied among offices and items. The temporary occupier was not observed on all items touched. In most instances, when detected, the temporary occupier was known to have touched the surface at some stage. Therefore, where one is seeking to collect samples that may detect a temporary user of a space, it is advisable to target several potentially touched sites. A difference in methodologies applied from collection through to profiling appears to impact DNA yields and profile types. Ascertaining the impact of using different methodologies on the profiles generated from collected samples, requires further research. More research is also needed to generate data to help determine frequency estimates for different types of profiles given different user histories of an item or space.
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http://dx.doi.org/10.1016/j.fsigen.2019.102203DOI Listing
January 2020

DNAxs/DNAStatistX: Development and validation of a software suite for the data management and probabilistic interpretation of DNA profiles.

Forensic Sci Int Genet 2019 09 21;42:81-89. Epub 2019 Jun 21.

Netherlands Forensic Institute, Division of Biological Traces, Laan van Ypenburg 6, 2497GB, The Hague, the Netherlands. Electronic address:

The data management, interpretation and comparison of sets of DNA profiles can be complex, time-consuming and error-prone when performed manually. This, combined with the growing numbers of genetic markers in forensic identification systems calls for expert systems that can automatically compare genotyping results within (large) sets of DNA profiles and assist in profile interpretation. To that aim, we developed a user-friendly software program or DNA eXpert System that is denoted DNAxs. This software includes features to view, infer and match autosomal short tandem repeat profiles with connectivity to up and downstream software programs. Furthermore, DNAxs has imbedded the 'DNAStatistX' module, a statistical library that contains a probabilistic algorithm to calculate likelihood ratios (LRs). This algorithm is largely based on the source code of the quantitative probabilistic genotyping system EuroForMix [1]. The statistical library, DNAStatistX, supports parallel computing which can be delegated to a computer cluster and enables automated queuing of requested LR calculations. DNAStatistX is written in Java and is accessible separately or via DNAxs. Using true and non-contributors to DNA profiles with up to four contributors, the DNAStatistX accuracy and precision were assessed by comparing the DNAStatistX results to those of EuroForMix. Results were the same up to rare differences that could be attributed to the different optimizers used in both software programs. Implementation of dye specific detection thresholds resulted in larger likelihood values and thus a better explanation of the data used in this study. Furthermore, processing time, robustness of DNAStatistX results and the circumstances under which model validations failed were examined. Finally, guidelines for application of the software are shared as an example. The DNAxs software is future-proof as it applies a modular approach by which novel functionalities can be incorporated.
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http://dx.doi.org/10.1016/j.fsigen.2019.06.015DOI Listing
September 2019

Assessment of the transfer, persistence, prevalence and recovery of DNA traces from clothing: An inter-laboratory study on worn upper garments.

Forensic Sci Int Genet 2019 09 17;42:56-68. Epub 2019 Jun 17.

Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, Australia; School of Molecular Sciences, La Trobe University, Bundoora, Australia.

Among the various items recovered from crime scenes or persons involved in a crime event, clothing items are commonly encountered and submitted for forensic DNA sampling. Depending on the case circumstances and the activity-of-interest, sampling of the garment may concentrate on collecting DNA from the wearer, or from one or more offenders who have allegedly contacted the item and/or wearer. Relative to the targeted DNA, background DNA already residing on the item from previous contacts, or transferred during or after the crime event, may also be collected during sampling and observed in the resultant DNA profile. Given our limited understanding of how, and from where, background DNA is derived on clothing, research on the transfer, persistence, prevalence, and recovery (TPPR) of DNA traces from upper garments was conducted by four laboratories. Samples were collected from several areas of two garments, each worn on separate working or non-working days and individually owned by four individuals from each of the four laboratories, and processed from DNA extraction through to profiling. Questionnaires documented activities relating to the garment prior to and during wearing, and reference profiles were obtained from the wearer and their close associates identified in the questionnaire. Among the 448 profiles generated, variation in the DNA quantity, composition of the profiles, and inclusion/exclusion of the wearer and their close associates was observed among the collaborating laboratories, participants, garments worn on different occasions, and garment areas sampled.
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http://dx.doi.org/10.1016/j.fsigen.2019.06.011DOI Listing
September 2019

An inter-laboratory comparison study on transfer, persistence and recovery of DNA from cable ties.

Forensic Sci Int Genet 2017 11 19;31:95-104. Epub 2017 Aug 19.

Division Biological Traces, Netherlands Forensic Institute, P.O. Box 24044, 2490 AA, The Hague, The Netherlands.

To address questions on the activity that led to the deposition of biological traces in a particular case, general information on the probabilities of transfer, persistence and recovery of cellular material in relevant scenarios is necessary. These figures may be derived from experimental data described in forensic literature when conditions relevant to the case were included. The experimental methodology regarding sampling, DNA extraction, DNA typing and profile interpretation that were used to generate these published data may differ from those applied in the case and thus the applicability of the literature data may be questioned. To assess the level of variability that different laboratories obtain when similar exhibits are analysed, we performed an inter-laboratory study between four partner laboratories. Five sets of 20 cable ties bound by different volunteers were distributed to the participating laboratories and sampled and processed according to the in-house protocols. Differences were found for the amount of retrieved DNA, as well as for the reportability and composition of the DNA profiles. These differences also resulted in different probabilities of transfer, persistence and recovery for each laboratory. Nevertheless, when applied to a case example, these differences resulted in similar assignments of weight of evidence given activity-level propositions.
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http://dx.doi.org/10.1016/j.fsigen.2017.08.015DOI Listing
November 2017