Forensic DNA analysis of sexual assault evidence requires unambiguous differentiation of DNA profiles in mixed samples. To investigate the feasibility of magnetic bead-based separation of sperm from cell mixtures using a monoclonal antibody against MOSPD3 (motile sperm domain-containing protein 3), 30 cell samples were prepared by mixing 10(4) female buccal epithelial cells with sperm cells of varying densities (10(3), 10(4), or 10(5) cells/mL). Western blot and immunofluorescence assays showed that MOSPD3 was detectable on the membrane of sperm cells, but not in buccal epithelial cells. After biotinylated MOSPD3 antibody was incubated successively with the prepared cell mixtures and avidin-coated magnetic beads, microscopic observation revealed that each sperm cell was bound by two or more magnetic beads, in the head, neck, mid-piece, or flagellum. A full single-source short tandem repeat profile could be obtained in 80% of mixed samples containing 10(3) sperm cells/mL and in all samples containing ≥10(4) sperm cells/mL. For dried vaginal swab specimens, the rate of successful detection was 100% in both flocked and cotton swabs preserved for 1 day, 87.5% in flocked swabs and 40% in cotton swabs preserved for 3 days, and 40% in flocked swabs and 16.67% in cotton swabs preserved for 10 days. Our findings suggest that immunomagnetic bead-based separation is potentially a promising alternative to conventional methods for isolating sperm cells from mixed forensic samples.

Variation in the type of tissue that larvae feed on can produce marked differences in developmental rate and body size, which can compromise predictions of minimum postmortem interval. A series of experiments were conducted to investigate the effect of fat content in the diet on larval growth in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae), an important forensic blowfly species in China. Bionomical parameters such as body size, development time, mortality, and sex ratio were observed. The results indicated that fat content in the diet has a dramatic effect on the body size and larval development. More dietary fat content was beneficial for development of larvae in first and early second instar. But it was adverse in the later third instar. Significantly, a high-fat diet resulted in increased development rates and the production of undersized larvae and adults. Overall mortality of larvae and pupa was higher when more fat was added to the diet, but sex ratio of adults was not negatively affected. This study highlights that the fat content in the diet should be considered in the entomological research and forensic application when estimating minimum postmortem interval on the basis of larval body size and developmental stage.

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