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Rapid STR Prescreening of Forensic Samples at the Crime Scene

NCJ Number
Date Published
February 2011
93 pages
This project's goals were to continue development of a unique melt-based approach to STR (Short Tandem Repeat) genotyping (dpFRET); to integrate and test that approach for compatibility with existing microfluidic extraction, amplification, and melt subcircuits; and to determine applicability for forensic applications.
The overall objective achieved by this project was the overcoming of difficulties associated with capillary- electrophoresis (CE)-based STR profiles that act as a barrier to rapid objective prescreening of probative samples at the crime scene. The achievement of project goals resulted in the simplification of converting laboratory protocols for portability, mainly by eliminating the many challenges associated with capillary electrophoresis (CE) size-based analysis. These challenges include biological/technological artifacts, added sample processing steps, and complex equipment demands required for portability. This project's validation phase demonstrated some of the advantages impossible with CE-based protocols. These advantages include higher sensitivity (5-25 picograms); elimination of pre-quantification; minimal or no apparent biological artifacts; applicability to smaller amplicons impossible with current assays; the ability to detect microvariants (SNPs); and transfer compatibility to a microfluidic platform. Through development and testing of the optimized assay with a microfluidic platform, the project achieved sample extraction from blood, PCR amplification, and melt-based allele detection, using a microfluidic-based subcircuit design. It is the transfer of this approach to a fully integrated microfluidic lab-on-a-card format that will permit processing and analysis of samples in an enclosed environment, thereby minimizing the chances for cross-contamination and providing a means for post-analysis archiving of DNA extracts for follow-on laboratory testing of probative samples. The project demonstrated the successful generation of a classic CE profile 18 months after archiving extracted DNA. This validated approach produces a preliminary profile at the scene and enables laboratory analysis of the probative samples without the need for additional sample extraction. 4 tables, 55 figures, and 23 references

Date Published: February 1, 2011