Illuminating touch deposits through cellular characterization of hand rinses and body fluids with nucleic acid fluorescence

• Published in: Forensic science international : genetics 2020-05, Vol.46, p.102269, Article 102269
• Main Authors: Burrill, Julia, Daniel, Barbara, Frascione, Nunzianda
• Format: Article
• Language: English
• Subjects: Body fluids; Cells, Cultured; Cellular content; DNA Fingerprinting; DNA localization; Flow Cytometry; Fluorescence; Fluorescent Dyes; Forensic Genetics - methods; Hand Disinfection; Humans; Keratinocytes - chemistry; Microscopy; Nasal Mucosa - chemistry; Ophthalmic Solutions; Saliva - chemistry; Skin - cytology; Skin cells; Staining and Labeling; Touch; Touch DNA
• ISSN: 1872-4973; 1878-0326
• DOI: 10.1016/j.fsigen.2020.102269

•Cellular content distribution is consistent within an individual but varies between individuals.•Washed and unwashed hands yield similar cellular content distributions consisting mostly of corneocytes.•A distinct population of nucleated cells was not observed in washed or unwashed hand rinses.•Corneocytes stain positively for DNA with nucleic acid dyes using flow cytometry and microscopy despite lacking nuclei.•Small or fragmentary cells containing DNA make limited to negligible contributions to hand rinses’ cell content. Forensic DNA typing from touched or handled items in routine casework is increasing as the sensitivity of detection techniques improves. Our understanding of the cellular/acellular content of touch deposits and the origins of the DNA therein is still limited. This work explores the cellular content of rinses from washed and unwashed hands, as well as saliva, nasal and eye washes which could be sources of transferred DNA onto hands. Flow cytometry and microscopic examination were used to detect granularity, size and nucleic acid fluorescence data. Cellular content did not vary significantly within an individual, although some differences were observed between donors. Saliva contained populations of nucleated epithelia as well as smaller cells and debris, all positive for DNA. Hand rinses consisted almost entirely of anucleate corneocytes, many of which also stained positive for nucleic acids. These data raise questions about shed corneocyte DNA content previously assumed to be negligible.