1. Misinterpretation of sample contamination in a Hungarian casework
Gábor Kovács - Zsolt Pádár
Research Centre for Forensic Sciences and Criminology, Széchényi István University, Győr, Hungary
Introduction
The risk of contamination is a generally recognized and intensively researched field of forensic DNA. In spite of quality assurance systems, recommendations and regulations, this risk is always present even in routine casework as evidenced by this example from Hungary.
We examine and try to resolve the contradictions presented by the two interpretations, which originate from contamination of the remaining soft tissue.
A couple - J. K. M. and Z. K. – were murdered and buried by A. P. and his accomplices between and During the investigation procedure suspicions arose that another missing person in the city – J. Gy. – might also be a homicide victim. On an unknown – N. N. – male body was discovered and exhumed.
In the process of individualization of the N. N. body, parts of the corpse and the living putative relatives of N. N. were analyzed with STR multiplex kits and CE separations in two different laboratories (A and B). The first analysis in “Lab A” – an ISO accredited laboratory - used the soft tissues from N. N. bone sample. Based on the results, the first opinion excluded the biological relationship of N. N. with the putative mother, the second one excluded with the putative daughter.
The subsequent analysis of “Lab B” – a non accredited laboratory - used the soft tissue (muscle) parallel to the bone sample from the N. N. body. Based on the results, the second opinion supported the hypothesis of biological (maternal) relationship with high probability (W = 99,999%).
Methods
Results
Different results of Laboratories
Discussed profiles of „Lab A” in first opinions Discussed profiles of „Lab B” in subsequent opinions Undiscussed profiles of „Lab A” Repeated analysis of „Lab A” from bone sample
Electropherograms of questioned sample in „Lab A”
Conclusion
The risk of contamination must never be ignored in forensic examination
The evaluation of minor/major component of a mixed profile can lead wrong interpretation
Different and controversial results does hold genuine problem to be solved
Ignorance of undiscussed results may hide the truth
Accreditation is not always equal to a proper opinion
Conclusion of expert opinions requires pluralistic legal platform and background
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