Contamination during criminal investigation: Detecting police contamination and secondary DNA transfer from evidence bags

Fonneløp, Ane Elida; Johannessen, Helen; Egeland, Thore; Gill, Peter

doi:10.1016/j.fsigen.2016.04.003

Cited by 41 publications

(38 citation statements)

References 19 publications

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“…These contamination incidents can only be explained by one or more transfers involving unknown vectors and are thus considered as indirect. This value is higher than in recent studies, which reported possible indirect contamination incidents in about 35% of the cases [4,11]. The relative frequency of indirect laboratory contamination incidents is similar before (10/17) and after (3/4) the additional procedures suggesting that background DNA is still present in the laboratory.…”

Section: Resultscontrasting

confidence: 53%

“…Overall the number of contamination incidents detected during the three years after the implementation of additional contamination minimization procedures was lower than during the three years before these additional procedures (110 vs 150) suggesting an overall slight effect of these procedures ( Table 2; P > 0.05, Fisher's Exact test). Several factors such as the sensitivity of the STR profiling kits [1,4], characteristics of the sample (touch DNA vs other secretions), amount of DNA characterizing the sample [3,5], education of the staff or the effort made to look for contamination incidents (e.g. number of relevant profiles in the staff-index database) [3] could also influence the detection of contamination incidents.…”

Section: Resultsmentioning

confidence: 99%

“…Several procedures have recently been proposed to reduce the risk of DNA contamination incidents on both the crime scene and in the laboratory [1,[4][5][6][7][8][9]. Among these procedures, several are particularly adapted to the laboratory environment.…”

Section: Introductionmentioning

confidence: 99%

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Positive impact of DNA contamination minimization procedures taken within the laboratory

Basset

Castella

2019

Forensic Science International: Genetics

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A study of the impact of DNA contamination minimization procedures  Contamination minimization procedures significantly decrease contaminations  Minimization procedures should be implemented all along the chain of analysis 2 ABSTRACT DNA contamination incidents are one of the most frequent sources of error in forensic genetics and can have serious consequences. It is therefore essential to take measures to prevent these events and to monitor the real impact of contamination minimization procedures. In this study, we review and compare the number of contamination events detected on trace samples analyzed by the Forensic Genetic Unit (FGU) of the University Center of Legal Medicine in Switzerland before and after the implementation of new contamination minimization procedures. Interestingly, the number of contamination events by laboratory staff was significantly reduced by more than 70% after the implementation of the procedures. However, no significant change was observed for contamination events by police collaborators. This difference is likely to be explained by the differential impact of procedures taken in the laboratory and on crime scene. It suggests that the reduction observed for laboratory contamination incidents is due to the new procedures taken. In conclusion, our study highlights that taking appropriate measures is efficient and can reduce the number of contamination incidents. However, it is important that such contamination minimization procedures be implemented all along the chain of analysis of a stain (i.e. from crime scene to the laboratory).

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Section: Resultscontrasting

confidence: 53%

Section: Resultsmentioning

confidence: 99%

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Positive impact of DNA contamination minimization procedures taken within the laboratory

Basset

Castella

2019

Forensic Science International: Genetics

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“…With the current sensitivity of profiling STR kits, it is more common to detect minute amount of contaminating DNA left by persons collecting or analyzing crime scene traces [1][2][3]. These contaminations represent one of the most frequent source of error in forensic genetics and may have serious consequences on the result of an analysis [1,4].…”

Section: Introductionmentioning

confidence: 99%

Lessons from a study of DNA contaminations from police services and forensic laboratories in Switzerland

Basset

Castella

2018

Forensic Science International: Genetics

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In Switzerland, the DNA profiles of police officers collecting crime scene traces as well as forensic genetic laboratories employees are stored in the staff index of the national DNA database to detect potential contaminations. Our study aimed at making a national inventory of contaminations to better understand their origin and to make recommendations in order to decrease their occurrence. For this purpose, a retrospective questionnaire was sent to both police services and forensic genetic laboratories for each case where there was a contamination. Between 2011 and 2015, a total of 709 contaminations were detected. This represents a mean of 11.5 (9.6-13.4) contaminations per year per 1'000 profiles sent to the Swiss DNA database. Feedbacks were obtained from the police, the laboratory or both for 552/709 (78%) of the contaminations. Approximately 86% of these contaminations originated from police officers whereas only 11% were from genetic laboratories employees and 3% were associated to other sources (e.g. positive controls, stain-stain contaminations). Interestingly, a direct contact between the stain and the contaminant person occurred in only 51% of the laboratory contaminations whereas this number increased to 91% for police collaborators. The high level of indirect DNA transfer in laboratories might be explained by the presence of "DNA reservoirs" suggesting that cleaning procedures should be improved. At the police level, most contaminations originated from the person who collected the trace and likely occurred directly at the crime scene. Improving sampling practices could be beneficial to reduce these contaminations.

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“…[24] One effective strategy to overcome database contamination is the establishment of elimination databases, which can be crosschecked to eliminate unwanted DNA data. [58][59][60][61] Another strategy is routine integrity checks of loaded DNA data. [34] The presence of unwanted profiles on the database can mislead the police or delay the resolution of cases.…”

Section: Challenges Of the Pofa Implementationmentioning

confidence: 99%

The UK National DNA Database: Implementation of the Protection of Freedoms Act 2012

Amankwaa

McCartney²

2018

Forensic Science International

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In 2008, the European Court of Human Rights, in S and Marper v the United Kingdom, ruled that a retention regime that permits the indefinite retention of DNA records of both convicted and non-convicted ("innocent") individuals is disproportionate. The court noted that there was inadequate evidence to justify the retention of DNA records of the innocent. Since the Marper ruling, the laws governing the taking, use, and retention of forensic DNA in England and Wales have changed with the enactment of the Protection of Freedoms Act 2012 (PoFA). This Act, put briefly, permits the indefinite retention of DNA profiles of most convicted individuals and temporal retention for some first-time convicted minors and innocent individuals on the National DNA Database (NDNAD). The PoFA regime was implemented in October 2013. This paper examines ten post-implementation reports of the NDNAD Strategy Board (3), the NDNAD Ethics Group (3) and the Office of the Biometrics Commissioner (OBC) (4). Overall, the reports highlight a considerable improvement in the performance of the database, with a current match rate of 63.3%. Further, the new regime has strengthened the genetic privacy protection of UK citizens. The OBC reports detail implementation challenges ranging from technical, legal and procedural issues to sufficient understanding of the requirements of PoFA by police forces. Risks highlighted in these reports include the deletion of some "retainable" profiles, which could potentially lead to future crimes going undetected. A further risk is the illegal retention of some profiles from innocent individuals, which may lead to privacy issues and legal challenges. In conclusion, the PoFA regime appears to be working well, however, critical research is still needed to evaluate its overall efficacy compared to other retention regimes.

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Contamination during criminal investigation: Detecting police contamination and secondary DNA transfer from evidence bags

Cited by 41 publications

References 19 publications

Positive impact of DNA contamination minimization procedures taken within the laboratory

Positive impact of DNA contamination minimization procedures taken within the laboratory

Lessons from a study of DNA contaminations from police services and forensic laboratories in Switzerland

The UK National DNA Database: Implementation of the Protection of Freedoms Act 2012

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