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Capillary zone electrophoresis separation and collection of spermatozoa for the forensic analysis of sexual assault evidence

NCJ Number
Electrophoresis Dated: 2020
Date Published

This article reports the use of capillary zone electrophoresis for the separation of intact sperm from whole and lysed epithelial cells in the processing of sexual assault kits (SAKs).


The processing of sexual assault kits (SAKs) relies on the genetic analysis of material extracted from swabs collected from the assault victim. A vital step in producing an identifiable DNA profile of the perpetrator is the effective separation of perpetrator (sperm) and victim (epithelial) DNA that have been isolated from the collected evidence. In the procedure described in this article, the separated components are deposited into wells of a microtiter plate using a computer-controlled fraction collector, and quantitative PCR is used to verify the collection of sperm cells by targeted amplification of male DNA. Results are presented from simulated sexual assault samples that have been aged for up to 18 months, as well as vaginal swabs from authentic forensic kits. Components extracted from the vaginal swabs from the SAK comigrated with an aged semen sample at 6.25 ± 0.25 min. Epithelial cells migrated from 10-12 minutes, producing baseline resolution of the components. Sperm cells were collected in a microtiter plate for downstream analysis. (publisher abstract modified)

Date Published: January 1, 2020