Probabilistic approaches to interpreting two-person DNA mixtures from post-coital specimens

Rodriguez, Jae Joseph Russell B.; Bright, Jo‐Anne; Salvador, Jazelyn M.; Laude, Rita P.; Ungria, Maria Corazon A. De

doi:10.1016/j.forsciint.2019.04.037

Cited by 5 publications

(5 citation statements)

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“…Recommendations with defined parameters that are based on validated protocols and casework experience are needed to advance the country's capacity for sexual assault investigations. Our previous work addressed some aspects of DNA testing for sexual assault cases particularly DNA extraction procedures (Rodriguez et al 2017) and probabilistic methods to interpret mixtures (Rodriguez et al 2019) considering the dynamics of sexual assault investigations in the Philippines. In this study, we evaluated the sensitivity and specificity of presumptive and confirmatory tests for semen and assessed whether these could be incorporated into standard procedures for STR DNA typing.…”

Section: Discussionmentioning

confidence: 99%

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

Rodriguez

Calacal

Laude

et al. 2019

Egypt J Forensic Sci

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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.

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Section: Discussionmentioning

confidence: 99%

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

Rodriguez

Calacal

Laude

et al. 2019

Egypt J Forensic Sci

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“…Details on sample collection and processing can be found in Ref. [1]. Briefly, DNA samples were amplified using the PowerPlex® 21 system that targets 20 short tandem repeat (STR) loci then separated and detected using the AB® 3500 Genetic Analyzer (Thermo Fisher Scientific).…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Data on likelihood ratios of two-person DNA mixtures interpreted using semi- and fully continuous systems

et al. 2019

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In the paper, “Probabilistic approaches to interpreting two-person DNA mixtures from post-coital specimens” [1], we analysed 102 two-person DNA samples from simulated mixtures and male-female and male-male post-coital specimens. We report here data on profile characteristics of these samples and likelihood ratios (LRs) generated using semi- and fully continuous systems. Both log10 LRs from true and non-contributor tests are presented. These data may supplement studies comparing performance of different probabilistic systems for DNA evidence interpretation.

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“…Sexual assault cases prove to be a major challenge for forensic crime laboratories due to the mixture of victim DNA with perpetrator(s) DNA, which, therefore, requires a deconvolution of the contributors. With the newer STR chemistries already providing enhanced sensitivity to minor contributor alleles, mixtures are becoming increasingly complex, and thus deconvolution via probabilistic genotyping [105][106][107][108][109] is becoming more common. Until more literature is published on the benefits of more direct approaches compared to the deleterious and time-consuming traditional methods, forensic policies will not change to allow crime laboratories to use these advanced methods.…”

Section: Rapid Dnamentioning

confidence: 99%

Review of direct PCR and Rapid DNA approaches to streamline sexual assault kit testing

Harrel¹,

Holmes²

2022

Journal of Forensic Sciences

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Crime laboratories have been faced with large casework backlogs due to lengthy processing times, limited resources and scientists, and rising crime rates. Evidence related to sexual assault crimes, specifically sexual assault kits (SAKs), heavily contribute to the reported backlogs. Although more sensitive, faster chemistries and automated techniques have been implemented over the years, the traditional STR workflow remains relatively unchanged. Enhanced workflows such as direct PCR and Rapid DNA

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Probabilistic approaches to interpreting two-person DNA mixtures from post-coital specimens

Cited by 5 publications

References 36 publications

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

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

Data on likelihood ratios of two-person DNA mixtures interpreted using semi- and fully continuous systems

Review of direct PCR and Rapid DNA approaches to streamline sexual assault kit testing

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