ABSTRACT
Millions of biological samples, including cells, viruses, and DNA/RNA, are stored every year for diagnostics, research, and forensic science. DNA extracts from forensic evidence samples such as hair, bones, teeth, and sexual assault evidence may contain less than 100 pg of DNA (Gill 2001; Gill et al. 2000; Phipps and Petricevic 2007; Smith and Ballantyne 2007). Low DNA yields may be due to damage (Budowle et al. 2005; Coble and Butler 2005; Irwin et al. 2007) or degradation (Eichmann and Parson 2008; Hill et al. 2008; Irwin et al. 2007); small cell numbers found in low copy number (LCN) or “touch” samples (Balogh et al. 2003; Budowle et al. 2009; Gill 2001; Gill et al. 2000; Hanson and Ballantyne 2005; Irwin et al. 2007; Kita et al. 2008; Kloosterman and Kersbergen 2003); oligospermic (Sibille et al. 2002) or aspermic perpetrators (Shewale et al. 2003); or low male DNA from extended interval postcoital samples in sexual assault cases (Hall and Ballantyne 2003). Trace biological evidence (e.g., ngerprints and touch evidence) may provide low yields (Balogh et al. 2003; Kita et al. 2008; Lagoa et al. 2008; Schulz and Reichert 2002; van Oorschot and Jones 1997; Wickenheiser 2002). Biological evidence may be consumed with the result that the DNA extracts may be the only remaining genomic resource to retest and test with new technologies for retrospective and prospective testing. Optimal storage of DNA is therefore critical to retrospective (retesting) or prospective (downstream analysis with additional or new genetic markers) testing (Clabaugh et al. 2007; Larsen and Lee 2005; Lee et al. 2012).
