The Mezzo – Employees have different levels of education (one lab director lamented that the newer FS graduates don’t have the math and analytical skills necessary to interpret the findings, so that they implemented another process where senior people always look at all results). Also, training within institutions with workloads and employee barriers diminishes accuracy of outcomes. We can thank the rape-kit backlog for the stresses on the laboratories and going straight to DNA detection, without determining the substance (AP and X-mas Tree Stain) is problematic (just a fact, not an opinion). With different skill levels in different labs with different acceptable thresholds, you can see that there is room for different interpretations, especially with AP color changes (yes, females have AP too, just lower amounts). Labs often use different reporting forms and same information is reported differently. Forms often report “sperm fraction” without validating “sperm” is present with AP, P30 (prostatic enzyme test) or Xmas Tree cellular stain on a slide. ...and that is a local organizational decision, based on financial and personnel resources.
The Micro – contamination and unequal distribution of the sample across the sampling device (I’m assuming it was 1 – 2 cotton tipped applicators) is difficult to divide when collection technique contributes to finding evidence too. Anal swabs are particularly difficult since the folds retain “dribble” forever! So, if there were scant amounts in/on the patient, and scant amounts in one side of the collection device, the division where the actual evidence on a sample location is unknown provides opportunity for one lab to find and another not. Another micro aspect is non-lab persons interpreting the results that may not fully understand AP, P30, and slide staining, and then finding a report that says “sperm fraction present” (and this finding is not necessarily sperm, it could be epithelial cells), and if the only “sperm” found is in the “sperm fraction” that is not necessarily sperm. (Call if you want more explanation.) Last, male fraction is found with contamination – lots of literature about contamination from everything, including lab personnel and partners of collectors!
So, this is a little explanation about why one lab finds, and another lab doesn’t find “sperm.” Importantly, it is not an RN role to determine how or why sperm is found or not. Even I, with my decade of DNA research, don’t offer opinion to the court. I teach lawyers to learn about the gaps, and they ask the questions to the laboratory personnel, including administration.
I think you will agree with me that research that addresses the explanation is necessary... Feel free to call if you have other questions and join the Academy of Forensic Nursing where scholars discuss these types of topics routinely.
Patricia M. Speck, DNSc, CRNP, FNP-BC, DF-IAFN, FAAFS, DF-AFN, FAAN