School of Medical Sciences Forensics: Identification of Vaginal Epithelial Cells

When examining exhibits from a sexual assault case, forensic scientists aim to obtain evidence that will support or refute an allegation of non-consensual sexual intercourse. Evidence may be recovered as trace evidence or body fluid stains from the victim, the suspect or the crime scene.

Case example:

It has been alleged that a bottle has been used to sexually violate a complainant, Ms X. Samples are collected from the bottle and a DNA profile matching Ms X is found.

The prosecution may allege that the DNA is vaginal in origin, whereas the defence may assert that this DNA is on the bottle because Ms X handled or drank from the bottle, not because it was transferred during a sexual act.

The specific identification of vaginal epithelial cells on the bottle would thus support the allegation of sexual assault and provide important probative evidence.

Claire French at work in the lab.

In forensic science there is a clear demand for a method to conclusively distinguish between skin, buccal (cheek) and vaginal epithelial cells.

Skin cells can be detected since they lack nuclei, however both buccal and vaginal cells are morphologically indistinguishable from each other. To our knowledge there is currently no conclusive test to distinguish between these three cell types.

Our group is focused on developing a method for distinguishing between these cell types using histological and immunohistological approaches that do not affect DNA integrity, and are therefore compatible with subsequent DNA profiling techniques.

Cell smears which have been fixed in methanol and stained with Dane’s stain allow differentiation between skin, buccal and vaginal cells.

People involved:

Claire French (PhD student, 2009)
Dr Sue McGlashan (PI)
Assoc Professor Cynthia Jensen (PI)
Ms Sue Vintiner, Senior Forensic Scientist, ESR
Dr Douglas Elliot, Senior Forensic Scientist, ESR
Mrs Sarah Paterson (MSc student, 2004)