Integrating presumptive and confirmatory semen tests into DNA profiling of sexual assault evidence: a Philippine example

Abstract

Background: In sexual assault casework, the detection of semen on a sample supports an allegation of sexual contact and indicates the presence of DNA from a male source. Ideally, techniques employed should demonstrate high sensitivity and specificity and should be compatible with standard DNA typing procedures. To contribute recommendations for routine DNA tests of sexual assault cases in the Philippines, we evaluated the RSID TM-Semen, an immunochromatographic test for human semenogelin (Sg), in parallel with the alternate light source (ALS) method using Mini BLUMAXX™ III and the acid phosphatase (AP) test using Seminal Fluid DISCHAPS TM. Results: The ALS detected semen diluted until 5% (v/v) fluid, whereas the AP assay was sensitive down to 0.5% (v/v). Non-blood-containing stains were visible under blue light except on dark-colored cloth. All semen-containing fluids including post-ejaculatory urine tested positive for AP and Sg. RSID TM-Semen was sensitive down to 0.5 nL of semen; did not cross-react with blood, saliva, and female urine; and successfully detected Sg on the majority of post-coital samples tested. Complete short tandem repeat (STR) profiles of the semen donors were generated for most samples incubated in the RSID TM-Universal Buffer (UB). However, we report an extraction efficiency of 15% for UB which can lead to partial profiles in already compromised samples. Conclusion: We recommend the use of ALS in visualizing stains present on surfaces and the AP test on bloodstained materials. These presumptive tests should be followed by RSID TM-Semen test to confirm the presence of semen prior to DNA profiling.

An integrated system for forensic DNA testing of sexual assault cases in the Philippines

“…In our previous work [ [10] , [11] , [12] ], we selected procedures that are already established in forensic practice and are relatively inexpensive considering the limited resources of Philippine laboratories. We evaluated their use in male-female and male-male post-coital samples.…”

“…The remaining buffer extract may be directly used as starting material for DNA extraction. While sample incubation in the buffer is expected to reduce DNA recovery, a full profile of the semen contributor resulted in the majority of swabs and stains we tested [ 10 ].…”

“…Semen negative samples do not rule out sexual penetration and may still generate the non-victim’s DNA profile. When there are no other semen positive specimens available, semen negative samples should still proceed to extraction [ 10 ].…”

“…However, molds will likely develop on anal swabs stored in ambient conditions which is warm and humid in the Philippines for most of the year. Mold growth was found to inhibit the detection of semen and resulted in partial DNA profiles [ 10 ]. Hence, we recommend the immediate processing of anal swabs when possible.…”

The effectiveness of a sexual assault nurse examiner-grounding program (SANE-GP) on knowledge, skill and practice regarding sexual assault examination (SAE) among nurses working in a tertiary care hospital in Udupi district, India: A study protocol

“…These include positioning and examination of the client, obtaining high-quality specimens, identifying and reporting genital-anal injuries after sexual assault, comparing the injuries of consensual and non-consensual intercourse, identifying and collecting traces from the fingernail and other materials for the DNA analysis of the aggressor and employing DNA evidence in sexual offence cases to aid the identification of suspects, movement of forensic evidence and chain of custody, analysing and preventing drug-facilitated crimes against women, usage of photo colposcopy to identify hymenal transections and other injuries in children and adult females, simulation, forensic photography, bite-mark identification, handling vicarious trauma and mindfulness based interventions for better coping. Peer support is also essential for nurses to be able to cope with the demands of working in such situations (Drake and Adams, 2015;Gharedaghi et al, 2018;Yesodharan et al, 2018Yesodharan et al, , 2021Rodriguez et al, 2019;Usman et al, 2019;Yassa and Badea, 2019;McAllister and Vennum, 2021;Zweig et al, 2021).…”