The importance of male underwear in cases of alleged sexual assault.

The potential evidential value of male underwear in cases of alleged sexual assault is often overlooked. Male underwear can be a critical item in the investigation of alleged sexual assaults. Body fluids/DNA, which may transfer to the penis during sexual contact, may in turn transfer to the inside front of the underwear, and persist for months or years, provided the underwear are not washed. Here, we demonstrate how the case circumstances drive the sampling strategy of male underwear, in order to maximize the effectiveness of the forensic analysis. Sampling considerations including recovery methods and sampling sequence are discussed, and a methodical examination strategy of male underwear is proposed. To highlight the pertinence of male underwear to the investigation of alleged sexual assaults, three real-life cases are discussed, in which male underwear were examined for multiple body fluids/DNA, and the findings obtained proved evidentially significant. The different cases demonstrate the versatility of male underwear examination in situations, where different body fluids and DNA may transfer based on the specific allegation, and emphasize how targeted sampling can allow the scientist to assess the probability of the findings based on two competing propositions. Accurate sampling strategies are imperative for robust probability assignment in evaluative reporting of scientific findings.

Wearer and non-wearer DNA on the collars and cuffs of upper garments of worn clothing.

During an investigation, the question of interest might be whether or not a person has worn a given garment. Wearer DNA studies have contributed to our knowledge and understanding of DNA transfer and persistence on items of worn clothing. However, there is currently no extensive dataset on DNA profiling outcomes from a variety of upper garments. Therefore we investigated the DNA profiling outcomes from the collars and/or cuffs of forty-four upper garments of worn clothing and determined the quantity of wearer and non-wearer DNA recovered. Interpretable DNA profiles were more likely to be obtained from collars than cuffs (84% versus 71%). The wearer was detected in all interpretable profiles and a major profile corresponding to the wearer was the most common outcome from both collar and cuff samples (48% and 50%, respectively). There was large variation in the amount of wearer DNA recovered and the average recovered was approximately 20 ng. Usually more wearer DNA was found on collars than cuffs of the same garment and, on average, more non-wearer DNA was found on cuffs than collars. No DNA was recovered from the cuffs of two garments despite these garments being worn for three and four hours, respectively. On one occasion a non-wearer contributed more DNA to a cuff sample than the wearer. We found no correlation between wearing time and the amount of wearer DNA recovered which indicates that other factors (e.g. shedder status and/or the manner of contact between the garment and skin) have a greater influence, than wearing time, on the amount of DNA transferred. However, there was a positive correlation between wearing time and the likelihood of obtaining interpretable profiles. This work has generated data to support the evaluation of DNA evidence from clothing and we provide a case example to demonstrate this.

Probability of detection of DNA deposited by habitual wearer and/or the second individual who touched the garment.

Available literature on the detection of transferred DNA does not address the interpretation issues in relation to who wore rather than touched the garment. To acquire a greater knowledge of the rate of detectable wearer, toucher and background DNA, 63 males wore their own underpants for 12h. The inside-waistband was handled by one of 11 female volunteers for 15s. The waist-band was mini-taped and subjected to DNA profiling with the AMPFℓSTR(®) NGM SElect™ kit. The findings show that on worn garments the probability of observing reportable DNA profiles is 61.9%. The wearer was detected as a single profile or part of a mixed profile in 50.8% of samples. When the wearer was present in a mixture, he was always observed as the major contributor. The toucher was detected on 11.1% of underpants. Reportable background DNA (non-wearer and non-toucher) occurs in 14.3% of samples and may affect the assessment of who wore the garment. Greater knowledge of the frequency of detection of reportable wearer DNA and/or toucher allows scientists to evaluate the likelihood of observing a matching profile if an individual wore a garment rather than touched it in disputed case scenarios.

Background Levels of Salivary-α-amylase Plus Foreign DNA in Cases of Oral Intercourse: a Female Perspective.

Saliva plus DNA from a suspect is commonly encountered in sexual assault cases on bodily swabs. However, without background knowledge, the weight of this evidence is unknown. It may indicate the presence of saliva resulting from cunnilingus, or it may represent indirect transfer. In this study, females who refrained from cunnilingus donated 43 items of underwear and 19 vaginal swabs. The samples were subjected to Phadebas(®) , RSID(™) -Saliva and mRNA profiling and were subsequently DNA-profiled to determine the prevalence of background saliva in the female population. The results report that 15.8% of females who refrained from cunnilingus were positive for saliva and a further 10.5% also had DNA from unknown source(s). These findings of the rate of indirect transfer were evaluated with the Bayesian approach, and it was found that the evidence of saliva plus a high foreign DNA source adds moderately strong support to the allegation of cunnilingus.

Oral intercourse or secondary transfer? A Bayesian approach of salivary amylase and foreign DNA findings.

The Bayesian Approach allows forensic scientists to evaluate the significance of scientific evidence in light of two conflicting hypothesis. This aids the investigator to calculate a numerical value of the probability that the scientific findings support one hypothesis over conflicting opinions. In the case where oral intercourse is alleged, α-amylase, an indicator of saliva, is detected on penile swabs. The value of this finding is unknown as it may indicate the presence of saliva resulting from oral intercourse however it may also represent the presence of saliva due to innocent means such as background levels of salivary-α-amylase in the male population due to secondary transfer. Therefore, it is difficult to attach significance to this finding without background information and knowledge. A population study of the background levels of salivary-α-amylase was performed by analysing items of underwear worn under normal circumstances by 69 male volunteers. The Phadebas press test was used to screen the garments for amylase-containing stains and the positive areas were subjected to further confirmation of saliva by the RSID-Saliva kit. 44% of underwear screened had stains containing amylase. This study determined the background level of salivary-α-amylase and DNA on the inside front of male underwear which has potential implications on the interpretation of evidence in alleged oral intercourse.