The need for automation is limited when using a quick and inexpensive one-tube DNA extraction protocol for crime scene samples

Generally, simplified manual protocols can serve as a cost-effective alternative to sophisticated automation solutions. We have developed, validated and implemented a quick, inexpensive and efficient one-tube direct lysis DNA extraction protocol for the majority of our crime scene samples. The method includes one pipetting step, the addition of a lysis buffer based on Chelex beads, Proteinase K and Tween 20. After three incubation steps with vortexing in between, the sample is ready for downstream applications (DNA quantification and STR profiling). The amount of lysis buffer added varies between 200–1000 μL depending on the amount of carrier material in the tube. If needed the extract can be purified or concentrated using a filter device, in our case Amicon Ultra-2. Through in-house validation we show that the method is fit-for-purpose for application in casework for samples containing blood, saliva, shed cells and semen as it provides high DNA yields and high quality STR profiles. The method was implemented at the Swedish National Forensic Centre (NFC) in February 2018. During the first year more than 35,000 crime scene samples were extracted using the method, generating DNA yields equivalent to the previously used method. In conclusion, the need for automation of the DNA extraction process is limited when using a one-tube direct lysis protocol including only the addition of lysis buffer and no transferring steps. In addition it saves costs as there is no need for expensive pipetting robots or service fees and since the reagents used in this direct lysis protocol are relatively inexpensive.