| 1. |
- Steensma, Kristy, et al.
(författare)
-
An inter-laboratory comparison study on transfer, persistence and recovery of DNA from cable ties
- 2017
-
Ingår i: Forensic Science International. - : ELSEVIER IRELAND LTD. - 1872-4973 .- 1878-0326. ; 31, s. 95-104
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 2. |
- Szkuta, Bianca, et al.
(författare)
-
Assessment of the transfer, persistence, prevalence and recovery of DNA traces from clothing: An inter-laboratory study on worn upper garments
- 2019
-
Ingår i: Forensic Science International. - : ELSEVIER IRELAND LTD. - 1872-4973 .- 1878-0326. ; 42, s. 56-68
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 3. |
- Szkuta, Bianca, et al.
(författare)
-
DNA transfer to worn upper garments during different activities and contacts: An inter-laboratory study
- 2020
-
Ingår i: Forensic Science International. - : ELSEVIER IRELAND LTD. - 1872-4973 .- 1878-0326. ; 46
-
Tidskriftsartikel (refereegranskat)abstract
- 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 persons 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 persons space. Particular areas of the garment were more prone to acquiring the hugging partner or office owners 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.
|
|
