To be sure whether

the immediate staining on the microscope slides would lead to the detection of the same number of nuclei compared to the staining with 1 h incubation, the two check details staining methods were performed on the same hair roots and compared. Focus has been put on naturally shed hairs, mimicking forensic situations. There were no significant differences between the two staining methods (McNemar test, p = 1.00), except for one hair in which direct staining of the hair root on a microscope slide resulted in detection of less nuclei compared to the longer incubation method. Counting less than 20 nuclei, all hair roots but one resulted in full STR profiles. From the 49 hair roots without any visible nuclei, 3 resulted in a partial STR profile and 1 even in a full STR profile ( Table 2). One of the hair roots which resulted in a partial profile, showed presence of adhering material, presumably dandruff. Adhering material can contain DNA and could therefore result in a STR profile. In an optimal situation, hair roots without visible nuclei could be discarded. In 96% (94/98) of all cases where no nuclei were observed, no STR profile was obtained. However, in 4% of these cases, a full or partial STR profile could be obtained. Therefore, results of DAPI-staining should

always Autophagy inhibitor molecular weight be considered in function of the importance of the evidential value of the found hair. If the hair is the only biological evidence in the forensic case, one might consider to submit the hair to STR analysis anyway, even if the staining is considered to be negative. If necessary, multiple hair roots showing the same characteristics can be pooled for STR analysis. In case the hair root did not yield a STR profile, the remainder of the hair can still be submitted to mitochondrial DNA analysis [16] and [17]. However, as STR analysis has a higher discriminative power compared to mitochondrial DNA analysis, the former is preferred. Ten hairs plucked from 1 donor were collected using the tape lifting kit, subsequently removed from the all adhesive tape and directly

stained on microscope slides. In 8 of 10 cases, 21–50 nuclei were counted while in the remaining 2 cases, more than 50 nuclei were observed. In all cases, full STR profiles were obtained (data not shown). However, loss of nuclei after removing the hair root from the adhesive tape could be observed as the adhesive tape was re-examined under the fluorescence microscope and nuclei were found on the tape. Therefore, if adhesive tapes are used for collecting hairs from a crime scene, it can be interesting for STR analysis to include that part of the tape where the hair root was located. The presented fast screening method was applied in 36 forensic cases in which 279 hair roots were stained with DAPI directly on microscope slides (part II). 263 hair roots were quoted as negative.