The Effect of the Methods for Detecting Blood Fingerprints on STR Typing

Abstract

In Japan, blood fingerprints found at crime scenes are photographed and transferred to a Pap or BB sheet. The transferred fingerprints are, if necessary, enhanced by a solution of tetramethylbenzidine (TMB) or leucomalachite green (LMG). The effects of TMB or LMG on short tandem repeat (STR) typing have been studied. However, the total effects of blood fingerprints detection methods on subsequent STR typing have not been investigated enough. In this study, 3 μl of blood and 20 μl of saliva samples smeared on glass slides were transferred to a Pap or BB sheet, transferred to a BB sheet and applied with TMG or LMG solution, and only sprayed with TMG or LMG solution. DNA was extracted by an EZ-1 DNA Investigator kit or by a QIAamp DNA Investigator kit. The quantity of DNA was measured by real-time PCR assay and STR typing was performed. The Pap sheet-transferred portions of the samples showed no STR profiles, regardless of the DNA extraction kits. On the other hand, the BB sheet-transferred portions showed full STR profiles in all the samples. The residual portions on the glass slide that had not been transferred to Pap or BB sheets, showed full STR profiles in most of the samples. The QIAamp kit had a tendency to provide a higher quantity of DNA than the EZ-1 kit. TMB hardly or slightly reduced the quantity of DNA, but full STR profiles were still obtained. The application of LMG to the BB-sheet transferred portions drastically reduced the quantity of DNA, and affected STR typing adversely. The spraying of LMG on the samples on glass slides slightly reduced the quantity of DNA, but gave full STR profiles. It was recommended that STR typing be performed from residual portions of samples that have not been transferred to Pap or BB sheets.