Automating the Forensic Analysis of Nuclear DNA: The FBI's Research and Development Initiative
In the United States, there is a substantial backlog of samples requiring short tandem repeat (STR) DNA marker analysis. Approximately 200,000 to 300,000 collected convicted offender samples (U.S. Department of Justice 2003) and more than 540,000 evidentiary samples where there is no suspect (Attorney General's Report on the DNA Evidence Backlog 2004) currently remain to be analyzed nationwide. Additionally, 500,000 to 1,000,000 authorized convicted offender samples have not yet been collected (U.S. Department of Justice 2003).
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To address this issue, Public Law 106-546, DNA Analysis Backlog Elimination Act of 2000, was enacted on December 21, 2000. This law authorized $170,000,000 toward reducing the backlog (DNA Analysis Backlog Elimination Act of 2000).
* $15,000,000 was appropriated in 2001 through 2003 for DNA analysis of samples to be included in the Combined DNA Index System (CODIS), the nationwide DNA database.
* $25,000,000 to $50,000,000 was appropriated in 2001 through 2004 for DNA analysis of samples from crime scenes and to increase the capability of public laboratories to carry out DNA analyses.
The intent of this spending was to eliminate the backlog of samples requiring STR DNA analysis by providing additional manpower and instrumentation for use with existing nuclear DNA analysis technologies.
Although existing nuclear DNA analysis technologies are valid and accurate, they are also labor-intensive and time-consuming. Introducing automation into the process flow for analysis of forensic biological samples would overcome the backlog problem and prevent its recurrence.
Identification of probative biological samples, the technical steps for typing the 13 core CODIS STR loci, and the interpretation of STR-analytical results and associated data quality review could all be automated. This would assist in achieving process quality and reproducibility.
During 2000 in support of the backlog reduction efforts, the FBI's Counterterrorism and Forensic Science Research Unit designed a research and development plan for automating the forensic analysis of biological evidence, which was funded by Congress in 2001. The FBI automation initiative is divided into three main areas--serology, the STR-typing process, and online data interpretation and quality assessment tools.
The goals for the serology initiative are to develop methods for the definitive identification of all forensically relevant biological stains and to automate the execution of these methods. Currently, biological samples deposited at crime scenes are identified by visual inspection, chemical reactions, enzymatic reactions, and standard immunological methods.
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Both a presumptive test and a confirmatory test are performed in the process, and these tests are conducted sequentially, requiring a new sample for each test (Ballantyne 2000). However, definitive tests do not exist for each of the frequently encountered body fluids (e.g., saliva or urine). Operational efficiency could be improved if a system existed whereby a complete panel of body fluid identification tests was performed simultaneously from a single sample (i.e., multiplexed analysis), and the identification system was amenable to automation.
The FBI recently initiated a project to develop a multiplexed immunoassay to identify forensically relevant body fluids. Novel antigens not previously used in forensic analysis will be interrogated using monoclonal antibodies, the most specific immunological reagents available.
The immunoassays will first be developed in a format suitable for individual high-throughput automation on a robotic liquid handler. Subsequently, the individual assays will be multiplexed and adapted to an as yet undecided detection platform. One possibility is a suspension array based on flow cytometry (Kellar and Iannone 2002; Nolan and Mandy 2001). …