An easily automated, closed-tube forensic DNA extraction procedure using a thermostable proteinase

Most standard procedures for extracting DNA from forensic substrates involve manipulations that expose the sample to potential contamination and which reduce yields. Furthermore, most methods require centrifugation and/or solvent extraction steps that render them difficult to automate. We describe a simple closed-tube DNA extraction procedure using a proteinase from the thermophilic Bacillus species EA1 that produces good DNA yields from a wide range of forensic substrates. The reaction is controlled by a temperature shift regime programmed into a thermal cycler and so eliminates the need for solvent extraction or column purification. The new method is ideally suited to forensic samples where exposure to extraneous contaminating DNA must be avoided. In addition, The simplicity of the procedure makes it suitable for automation.