Development of a Simulation Model to Assess the Impact of Contamination in Casework Using STRs

    Volume 49, Issue 3 (May 2004)

    ISSN: 0022-1198

    CODEN: JFSOAD

    Published Online: 10 March 2004

    Page Count: 7


    Kirkham, A
    Forensic Science Service, Trident Court, Solihull,

    Gill, P
    Forensic Science Service, Trident Court, Solihull,

    (Received 1 November 2003; accepted 19 January 2004)

    Abstract

    Because contamination is usually tube-specific, negative controls cannot give assurance that an associated batch of extracted casework material is contaminant-free. However, it is possible to use them to predict the level of overall (undetected) contamination that is processed by an operational DNA unit. A MATLAB®-based program was used to combine results of negative controls with actual casework DNA profiles to assess the probability that laboratory contaminants will give rise to reportable profiles (along with their likelihood ratios). Using data from an operational DNA unit as an example, it was demonstrated that the risk is inextricably linked to guidelines used to interpret DNA profiles. We have demonstrated how computer-based models can predict the levels of contamination expected in the process and, in addition, how the process can be made more robust by changing reporting guidelines. There is a need to compare DNA profiles against staff and plasticware elimination databases in order to determine sources of contamination. The likeliest outcome of a contamination event is false exclusion.


    Paper ID: JFS2003366

    DOI: 10.1520/JFS2003366

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    Title Development of a Simulation Model to Assess the Impact of Contamination in Casework Using STRs
    Symposium , 0000-00-00
    Committee E30