A textbook case of a differential lysis for male infidelity

Because of the absence of their sex life, the wife became suspicious about a heavily stained pair of her husbands underwear and contacted SSDI for a semen detection.  After a detailed discussion, the customer elected to proceed to having a differential lysis performed on the sample because a positive semen detection on male underwear is the normal outcome.

Tested Sample - Male Underwear

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DNA from epithelial cells can be removed using a procedure called a differential lysis, which takes advantage of unique properties associated with each cell type. The cells are removed from the suspected material by soaking them in a gentle solution.  Epithelial cell DNA (such as those found in vaginal fluid) is isolated under mild conditions that break open the epithelial cells but leave the sperm cells DNA intact.  The DNA in spermatozoa can then be extracted using a more harsh extraction procedure.

A textbox example of a perfect Differential Lysis (DL) was performed which is documented by the electropherograms shown below the summary report.

Upon completion of the DL, the customer concluded that the most likely suspect was her sister.  She obtained a chewed piece of gum from her sisters trashcan.  The gum profile perfectly matched the female fraction of the DL performed on his wife's underwear.  The customer had undeniable proof that her husband was having a sexual relationship with her sister.

Evidence 

The items to be tested are: R1-one piece of male underwear for differential lysis and R2-chewing gum for a control sample.  The gum matched the female profile found in his underwear.

Analysis 

Differential lysis, followed by DNA extraction, PCR and Genotyper was performed on a small section of R1-the male underwear containing the stain.  DNA extraction, PCR and Genotyper were performed on sample R2-chewing gum control sample. 

Results:
DNA ANALYSIS RESULTS: Allele and number of repeats

Conclusions: 

R1, the stain on the male underwear, is consistent with two contributors, one of which was a female contributor and one of which was a male contributor.  The profile from sample R2, chewing gum, was identical to the female fraction of sample R1. 

Differential Lysis Electropherograms

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