Detection of cellular material in lip-prints

We report on the visualization of cellular material within lip-prints using Diamond™ dye (DD). The transfer of cellular material via the lips can occur in cases of contact with food or drinking items as well as cases of alleged sexual assault involving oral contact. DD can effectively detect cellular material transferred by touch. Here we investigate if lip-prints can be detected and whether there is consistency within, or variability between, a person’s propensity to shed cells within lip-prints. Ten volunteers were asked to press their lips against a glass slide with medium pressure for 15 s after not eating or drinking for at least 30 min. Both upper and lower lips were observed, and all tests were performed in five replicates, giving in total 900 observed areas. Consistency in the amount of cellular material deposited by lip-prints for each of the 10 individuals was observed, with each individual being associated with a ‘lip shedder’ status between the extremes of heavy and light. The majority of females shed more cells than the majority of males. No correlation was observed between the lip-prints shedder-status compared to deposition of cellular material from a thumb. Further, no correlation was observed between lip morphology and the ‘lip shedder’ status. Visualization of cellular material was not affected by lip-balm but was adversely affected by cosmetics such as lipstick. This technique demonstrates the visualization of deposited cells from parts of the body other than fingers and how cellular material can be visualized allowing targeted collection of DNA.