The Use of Hemastix® and the Subsequent Lack of DNA Recovery Using the Promega DNA IQTM System
Following implementation of our automated process incorporating the Promega DNA IQTM system as a DNA extraction method, a large number of blood-containing exhibits failed to produce DNA. These exhibits had been tested with the Hemastix® reagent strip, commonly used by police investigators and forensic laboratories as a screening test for blood. Some exhibits were even tainted green following transfer of the presumptive test reagents onto the samples. A series of experiments were carried out to examine the effect of the Hemastix® chemistries on the DNA IQTM system. Our results indicate that one or more chemicals imbedded in the Hemastix® reagent strip severely reduce the ability to recover DNA from any suspected stain using the DNA IQTM magnetic bead technology. The 3,3′,5,5′-tetramethylbenzidine (TMB) used as the reporting dye appears to interact with the magnetic beads to prevent DNA recovery. Hydrogen peroxide does not seem to be involved. The Hemastix® chemistries do not interfere in any way with DNA extraction performed using phenol-chloroform. The incompatibility of the Hemastix® chemistries on the DNA IQTM system forced us to adopt an indirect approach using filter paper to carry out the presumptive test.
Document Type: Research Article
Affiliations: 1: Royal Canadian Mounted Police, National Forensic Services—Vancouver, Biology Services, 5201 Heather Street, Vancouver, BC, V5Z 3L7 Canada. 2: Royal Canadian Mounted Police, National Forensic Services—Ottawa, Biology Services, 1200 Vanier Parkway, Ottawa, ON, K1G 3M8 Canada. 3: Royal Canadian Mounted Police, National Services and Research, 1200 Vanier Parkway, Ottawa, ON, K1G 3M8 Canada.
Publication date: November 1, 2009