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Onofri M, Tommolini F, Severini S, Gambelunghe C, Lancia M, Carlini L, Carnevali E. Trace DNA Transfer in Co-Working Spaces: The Importance of Background DNA Analysis. Int J Mol Sci 2024; 25:2207. [PMID: 38396883 PMCID: PMC10888653 DOI: 10.3390/ijms25042207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 02/08/2024] [Accepted: 02/09/2024] [Indexed: 02/25/2024] Open
Abstract
The presence of background DNA (bgDNA) can hinder the evaluation of DNA evidence at the activity level, especially when the suspect is expected to be retrieved due to their habitual occupation of the investigated environment. Based on real-life casework circumstances, this study investigates the prevalence, composition, origin, and probable transfer routes of bgDNA found on personal items in situations where their owner and person of interest (POI) share the same workspace. Baseline values of bgDNA were evaluated on the participants' personal items. Secondary and higher degree transfer scenarios of non-self DNA deposition were also investigated. The DNA from co-workers and co-inhabiting partners can be recovered from an individual's personal belongings. Non-self DNA present on the hands and deposited on a sterile surface can generate uninformative profiles. The accumulation of foreign DNA on surfaces over time appears to be crucial for the recovery of comparable profiles, resulting in detectable further transfer onto other surfaces. For a thorough evaluation of touch DNA traces at the activity level, it is necessary to collect information not only about DNA transfer probabilities but also about the presence of the POI as part of the 'baseline' bgDNA of the substrates involved.
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Affiliation(s)
- Martina Onofri
- Forensic Sciences Laboratory, Section of Legal Medicine, Department of Medicine and Surgery, Santa Maria Hospital, University of Perugia, 05100 Terni, Italy; (F.T.); (S.S.); (E.C.)
- Section of Legal Medicine, Department of Medicine and Surgery, University of Perugia, 06123 Perugia, Italy; (C.G.); (M.L.); (L.C.)
| | - Federica Tommolini
- Forensic Sciences Laboratory, Section of Legal Medicine, Department of Medicine and Surgery, Santa Maria Hospital, University of Perugia, 05100 Terni, Italy; (F.T.); (S.S.); (E.C.)
| | - Simona Severini
- Forensic Sciences Laboratory, Section of Legal Medicine, Department of Medicine and Surgery, Santa Maria Hospital, University of Perugia, 05100 Terni, Italy; (F.T.); (S.S.); (E.C.)
| | - Cristiana Gambelunghe
- Section of Legal Medicine, Department of Medicine and Surgery, University of Perugia, 06123 Perugia, Italy; (C.G.); (M.L.); (L.C.)
| | - Massimo Lancia
- Section of Legal Medicine, Department of Medicine and Surgery, University of Perugia, 06123 Perugia, Italy; (C.G.); (M.L.); (L.C.)
| | - Luigi Carlini
- Section of Legal Medicine, Department of Medicine and Surgery, University of Perugia, 06123 Perugia, Italy; (C.G.); (M.L.); (L.C.)
| | - Eugenia Carnevali
- Forensic Sciences Laboratory, Section of Legal Medicine, Department of Medicine and Surgery, Santa Maria Hospital, University of Perugia, 05100 Terni, Italy; (F.T.); (S.S.); (E.C.)
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Reither JB, Taylor D, Szkuta B, van Oorschot RAH. Determining the number and size of background samples derived from an area adjacent to the target sample that provide the greatest support for a POI in a target sample. Forensic Sci Int Genet 2024; 68:102977. [PMID: 38000160 DOI: 10.1016/j.fsigen.2023.102977] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/10/2023] [Accepted: 11/06/2023] [Indexed: 11/26/2023]
Abstract
When sampling an item or surface for DNA originating from an action of interest, one is likely to collect DNA unrelated to the action of interest (background DNA). While adding to the complexity of a generated DNA profile, background DNA has been shown to aid in resolving the genotypes of contributors in a targeted sample, and where references of donors to the background DNA are not available, strengthen the LR supporting a person of interest contributing to the targeted sample. This is possible thanks to advances in probabilistic genotyping, where forensic labs are able to deconvolute complex DNA profiles to obtain lists of genotypes and their associated weights. Coupled with DBLR™, one can then compare multiple evidentiary profiles to each other to determine the contribution of common, but unknown, contributors. Here, we consider factors associated with taking background samples and whether one should collect multiple background samples that all relate to a single target sample, or if one should collect larger background samples rather than smaller samples. Background samples consisted of DNA accumulated on the items primarily by one or both occupants of a single household, while targeted samples were generated from touch deposits, or saliva deposits that had been left to air dry. Samples were collected from areas of various sizes, consisting of only the background, the target and the background directly beneath it, and the target and additional surrounding background. A broad range of DNA quantities were recovered, with larger background samples (400 cm2) yielding significantly more DNA than smaller background samples (30 cm2). Significant differences in DNA quantities between target samples were not observed. Generated DNA profiles were interpreted using STRmix™ and DBLR™, and where there was support for a common donor between the background and target sample, pairwise comparisons were performed to observe the effect on the LR supporting the target DNA donor contributing to the targeted sample when conditioning on one (or two) common donor between the targeted sample and 1-8 background samples. Multiple background samples gave significantly higher LRs compared to a single background sample, the larger sampled background area resulted in larger LR gains than the smaller areas, and four or more background samples reduced LR variability considerably. Here we provide recommendations for the minimum and ideal number of additional background samples that should be collected, and that several smaller samples may be more beneficial than a single larger sample.
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Affiliation(s)
- Jack B Reither
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3220, Australia; Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, VIC 3085, Australia.
| | - Duncan Taylor
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia; Forensic Science SA, GPO Box 2790, Adelaide, SA 5001, Australia
| | - Bianca Szkuta
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3220, Australia
| | - Roland A H van Oorschot
- Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, VIC 3085, Australia; School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, VIC 3086, Australia
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Sessa F, Pomara C, Esposito M, Grassi P, Cocimano G, Salerno M. Indirect DNA Transfer and Forensic Implications: A Literature Review. Genes (Basel) 2023; 14:2153. [PMID: 38136975 PMCID: PMC10742555 DOI: 10.3390/genes14122153] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 11/22/2023] [Accepted: 11/27/2023] [Indexed: 12/24/2023] Open
Abstract
Progress in DNA profiling techniques has made it possible to detect even the minimum amount of DNA at a crime scene (i.e., a complete DNA profile can be produced using as little as 100 pg of DNA, equivalent to only 15-20 human cells), leading to new defense strategies. While the evidence of a DNA trace is seldom challenged in court by a defendant's legal team, concerns are often raised about how the DNA was transferred to the location of the crime. This review aims to provide an up-to-date overview of the experimental work carried out focusing on indirect DNA transfer, analyzing each selected paper, the experimental method, the sampling technique, the extraction protocol, and the main results. Scopus and Web of Science databases were used as the search engines, including 49 papers. Based on the results of this review, one of the factors that influence secondary transfer is the amount of DNA shed by different individuals. Another factor is the type and duration of contact between individuals or objects (generally, more intimate or prolonged contact results in more DNA transfer). A third factor is the nature and quality of the DNA source. However, there are exceptions and variations depending on individual characteristics and environmental conditions. Considering that secondary transfer depends on multiple factors that interact with each other in unpredictable ways, it should be considered a complex and dynamic phenomenon that can affect forensic investigation in various ways, for example, placing a subject at a crime scene who has never been there. Correct methods and protocols are required to detect and prevent secondary transfer from compromising forensic evidence, as well as the correct interpretation through Bayesian networks. In this context, the definition of well-designed experimental studies combined with the use of new forensic techniques could improve our knowledge in this challenging field, reinforcing the value of DNA evidence in criminal trials.
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Affiliation(s)
- Francesco Sessa
- Department of Medical, Surgical and Advanced Technologies “G.F. Ingrassia”, University of Catania, 95121 Catania, Italy; (C.P.); (M.S.)
| | - Cristoforo Pomara
- Department of Medical, Surgical and Advanced Technologies “G.F. Ingrassia”, University of Catania, 95121 Catania, Italy; (C.P.); (M.S.)
| | | | - Patrizia Grassi
- “Vittorio Emanuele” Hospital, University of Catania, 95121 Catania, Italy;
| | - Giuseppe Cocimano
- Department of Mental and Physical Health and Preventive Medicine, University of Campania “Vanvitelli”, 80121 Napoli, Italy;
| | - Monica Salerno
- Department of Medical, Surgical and Advanced Technologies “G.F. Ingrassia”, University of Catania, 95121 Catania, Italy; (C.P.); (M.S.)
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Reither JB, Taylor D, Szkuta B, van Oorschot RA. Exploring how the LR of a POI in a target sample is impacted by awareness of the profile of the background derived from an area adjacent to the target sample. Forensic Sci Int Genet 2023; 65:102868. [DOI: 10.1016/j.fsigen.2023.102868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023]
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Reither JB, van Oorschot RAH, Durdle A, Szkuta B. DNA transfer to placed, stored, and handled drug packaging and knives in houses. Forensic Sci Int Genet 2023; 65:102888. [PMID: 37182457 DOI: 10.1016/j.fsigen.2023.102888] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 05/04/2023] [Accepted: 05/07/2023] [Indexed: 05/16/2023]
Abstract
Forensic laboratories often sample weapons and clip-seal plastic bags (CSPB) used to package illicit material for the purpose of identifying the handler(s). However, there may be other explanations as to how a person's DNA was transferred to such items. This may include an individual storing the item among their personal belongings for somebody else or the item being stored among their belongings without their knowledge. Here we investigate the direct transfer of DNA to knives and CSPB during handling and explore two feasible alternative explanations related to the indirect transfer of DNA to these items in residential environments. The handling of DNA-free items was performed by 10 individuals who were instructed, on separate occasions, to cut a foam board in half and fill a CSPB with a drug substitute. To explore indirect transfer, sets of these items were (a) placed on kitchen benches and coffee/dining tables for ∼1 min, or (b) stored for two days in kitchen and bedroom drawers within the homes of 10 individuals. After each of the three scenarios, samples were collected from the knife handle and blade, the body and seal of the CSPB, and the surface the items were placed on, the latter as a measure to gain insight into the presence of prevalent and/or background DNA. DNA transfer was observed under all three scenarios, though more frequently when items were handled or stored for 2 days, compared to when placed on a surface for ∼1 min. Under the latter scenario, DNA, if present, was below the level of detection in many samples and produced no profile, suggesting that detectable DNA transfer occurs to a lesser degree from static brief contacts. The study results and associated probabilities will assist forensic examiners with their interpretation of case circumstances regarding the transfer and recovery of DNA from these items.
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Affiliation(s)
- Jack B Reither
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3220, Australia; Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, VIC 3085, Australia.
| | - Roland A H van Oorschot
- Office of the Chief Forensic Scientist, Victoria Police Forensic Services Department, Macleod, VIC 3085, Australia; School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, VIC 3086, Australia
| | - Annalisa Durdle
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3220, Australia
| | - Bianca Szkuta
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3220, Australia
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Is there human DNA on cats. FORENSIC SCIENCE INTERNATIONAL GENETICS SUPPLEMENT SERIES 2022. [DOI: 10.1016/j.fsigss.2022.10.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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