Relationship of spermatoscopy, prostatic acid phosphatase activity and prostate-specific antigen (p30) assays with further DNA typing in forensic samples from rape cases

From crime scene to courtroom: A review of the current bioanalytical evidence workflows used in rape and sexual assault investigations in the United Kingdom

Sexual assault casework requires the collaboration of multiple agency staff to formalise an investigative pipeline running from crime scene to court. While the same could be said of many other forensic investigations, few require the additional support of health care staff and the combined forensic involvement of body-fluid examiners, DNA experts and analytical chemists. The sheer amount of collaborative effort between agencies is laid out through a detailed examination of the investigative workflow from crime scene to courtroom with each step in the pipelines detailed and discussed. Beginning with a review of sexual assault legislation in the United Kingdom this article details how sexual assault investigations are initiated by police and supported by sexual assault referral centre (SARC) staff who are often the first responders providing primary healthcare and patient support to victims while simultaneously collecting and assessing forensic evidence. Detailing the myriad of evidential material that can be documented and collected at the SARC, the review identifies and categorises key forensic tests to first detect and identify body-fluids recovered from evidence through to the secondary analysis of DNA to help identify the suspect. This review also focusses on the collection and analysis of biological material used to support the allegation that the sexual activity was non-consensual and provides a breakdown of common marks and trauma as well as a review of common analytical methods used to infer Drug Facilitated Sexual Assault (DFSA). The culmination of the investigative pipeline is discussed by reviewing the Rape and Serious Sexual Assault (RASSO) workflow used by the Crown Prosecution Service before providing our thoughts on the future of forensic analysis and possible changes to the described workflows.

Loop-mediated isothermal amplification assay for fluorescence analysis and lateral flow detection of male DNA

Male DNA screening is important in forensic investigations, such as sexual assault cases. Although quantitative real-time PCR is a robust method for detection of male DNA, it is time-consuming and labor-intensive. We herein report the development of a male DNA-targeted loop-mediated isothermal amplification (LAMP) assay that can be used for both laboratory-based fluorescence analysis and on-site lateral flow detection. The two detection systems are independent, but we streamlined the reaction before the detection by introducing a fluorescence probe and biotin-labeled primer into a single reaction. This allowed the evaluation of fluorescence signal followed by lateral flow detection. Both the fluorescence and lateral flow analyses detected as low as 10 pg of male DNA. We also integrated an alkaline lysis method with our LAMP assay. The direct assay successfully detected male DNA from forensic samples without purification. The workflow requires only <40 min for fluorescence analysis and <45 min for lateral flow detection. Furthermore, when combined with a lateral flow strip, this workflow does not require any sophisticated instruments. These findings suggest that our assay is a promising strategy for on-site male DNA screening as well as laboratory-based testing.

Specific fluorescent signatures for body fluid identification using fluorescence spectroscopy

Non-invasive, rapid, on-site detection and identification of body fluids is highly desired in forensic investigations. The use of fluorescence-based methods for body fluid identification, have so far remain relatively unexplored. As such, the fluorescent properties of semen, serum, urine, saliva and fingermarks over time were investigated, by means of fluorescence spectroscopy, to identify specific fluorescent signatures for body fluid identification. The samples were excited at 81 different excitation wavelengths ranging from 200 to 600 nm and for each excitation wavelength the emission was recorded between 220 and 700 nm. Subsequently, the total emitted fluorescence intensities of specific fluorescent signatures in the UV-visible range were summed and principal component analysis was performed to cluster the body fluids. Three combinations of four principal components allowed specific clustering of the body fluids, except for fingermarks. Blind testing showed that 71.4% of the unknown samples could be correctly identified. This pilot study shows that the fluorescent behavior of ageing body fluids can be used as a new non-invasive tool for body fluid identification, which can improve the current guidelines for the detection of body fluids in forensic practice and provide the robustness of methods that rely on fluorescence.

Optimization of novel loop-mediated isothermal amplification with colorimetric image analysis for forensic body fluid identification

Accurate presumptive and confirmatory test use for forensic body fluid identification is essential for gaining contextual information for crime scene investigators. Loop-mediated isothermal amplification (LAMP) is an ideal method for forensic body fluid identification because it is highly specific and generates multi-sized amplicon DNA, and successful amplification results can be read out colorimetrically. Here, we show preliminary data on a LAMP method that rapidly identifies body fluids including venous blood, semen, and saliva, based on colorimetric response and image analysis. The method is designed for easy implementation into forensic casework protocols with minimal disruption to DNA analysis. LAMP naturally increases target specificity due to the use of multiple primers for one target and mRNA targets were used for tissue and human specificity. With colorimetric detection as an inherent part of LAMP, samples that are positive or negative for any of the body fluids are readily identified by image capture and analysis, thus eliminating subjectivity. Results show by using the 3D-printed imaging system specific color ranges can be set for easy determination of body fluids. The resulting color change can be seen in <30 min using a universal temperature and primer concentration for all body fluids. This simple method and imaging system allow for minimal hands-on time with objective image analysis and presents a pathway for creating a new potential method for forensic body fluid identification.

A retrospective study of sexual offences in Zambia

Zambia has recently reported high incidences of sexual abuse against women and children. Zambian law categorises sexual offences into rape, defilement, incest and others, with defilement constituting the majority of the reported cases (>89%). Between 2010 and 2012, convictions of defilement cases were achieved in only 13% of cases reported to the police. DNA evidence has shown prominence in resolving crimes, specifically as an identification tool in sexual offences. Currently there is no empirical evidence describing the role of forensic evidence in sexual crimes in Zambia; as such a retrospective study was conducted to evaluate this between 2007 and 2014 (n = 1154). Only 14 (0.1%) of the cases had forensic samples collected in the form of a vaginal swab for semen analysis. In all cases where a suspect was identified (60%), identification was based on the witness/victim testimonies, and in no case, was forensic DNA evidence used to assist in identification or corroborate the testimonies. Overall, 28.1% of cases were taken to court and the conviction rate was 12.4%. These findings support the use of employing DNA evidence in sexual offence cases to aid the identification of suspects, which is hypothesised to increase the number of cases prosecuted in Zambia.

A capillary electrophoresis method for identifying forensically relevant body fluids using miRNAs

Body fluid identification (BFID) can provide crucial information during the course of an investigation. In recent years, microRNAs (miRNAs) have shown considerable body fluid specificity, are able to be co-extracted with DNA, and their small size (18-25 nucleotides) make them ideal for analyzing highly degraded forensic samples. In this study, we designed a preliminary 8-marker system for BFID including an endogenous reference gene (let-7g) to differentiate between venous blood (miR-451a and miR-142-3p), menstrual blood (miR-141-3p and miR-412-3p), semen (miR-891a and miR-10b), and saliva (miR-205) using a capillary electrophoresis approach. This panel uses a linear primer system in order to incorporate additional miRNA markers by forming a multiplex system. The miRNA system was able to distinguish between venous blood, menstrual blood, semen, and saliva using a rudimentary data interpretation strategy. All STR amplifications from co-extracted DNA yielded complete profiles from human identification purposes.

An Optimized Centrifugal Method for Separation of Semen from Superabsorbent Polymers for Forensic Analysis

Connection of a perpetrator to a sexual assault is best performed through the confirmed presence of semen, thereby proving sexual contact. Evidentiary items can include sanitary napkins or diapers containing superabsorbent polymers (SAPs), complicating spermatozoa visualization and DNA analysis. In this report, we evaluated the impact of SAPS on the current forensic DNA workflow, developing an efficient centrifugal protocol for separating spermatozoa from SAP material. The optimized filtration method was compared to common practices of excising the top layer only, resulting in significantly higher sperm yields when a core sample of the substrate was taken. Direct isolation of the SAP-containing materials without filtering resulted in 20% sample failure; additionally, SAP material was observed in the final eluted DNA samples, causing physical interference. Thus, use of the described centrifugal-filtering method is a simple preliminary step that improves spermatozoa visualization and enables more consistent DNA yields, while also avoiding SAP interference.

Cell type determination and association with the DNA donor

In forensic casework, evidence regarding the type of cell material contained in a stain can be crucial in determining what happened. For example, a DNA match in a sexual offense can become substantially more incriminating when there is evidence supporting that semen cells are present. Besides the question which cell types are present in a sample, also the question who donated what (association) is very relevant. This question is surprisingly difficult, even for stains with a single donor. The evidential value of a DNA profile needs to be combined with knowledge regarding the specificity and sensitivity of cell type tests. This, together with prior probabilities for the different donor-cell type combinations, determines the most likely combination. We present a Bayesian network that can assist in associating donors and cell types. A literature overview on the sensitivity and specificity of three cell type tests (PSA test for seminal fluid, RSID saliva and RSID semen) is helpful in assigning conditional probabilities. The Bayesian network is linked with a software package for interpreting mixed DNA profiles. This allows for a sensitivity analysis that shows to what extent the conclusion depends on the quantity of available research data. This can aid in making decisions regarding further research. It is shown that the common assumption that an individual (e.g. the victim) is one of the donors in a mixed DNA profile can have unwanted consequences for the association between donors and cell types.

Diagnostic value of PSA and AP tests for the detection of spermatozoa in postmortem swabs from the genital and anal region in males

The aim of this study was to clarify whether positive results for prostate-specific antigen (PSA) and acid phosphatase (AP) occur in postmortem swabs from the genito-anal region in males (n = 80; 4 regions) and females (n = 20; 3 regions) and to calculate the positive predictive value (PPV) concerning the presence of spermatozoa. In male subjects, the highest incidence of positive test results was found in urethral swabs (PSA 76%, AP 71%) and the lowest frequencies appeared in perianal and rectal swabs (15-20%). Microscopic evaluation for spermatozoa was positive between 39% in urethral swabs and 1% in rectal swabs. PPV regarding positive identification of spermatozoa was 33.3% for PSA and 31.5% for AP. The combination of both tests yielded a PPV of 38.2%. In female cases, no spermatozoa were identified, and one case was PSA- and AP-positive in perianal swabs. Our findings indicate that PSA and AP tests are of limited value for the postmortem detection of spermatozoa in male subjects.

Differentiation of mixed biological traces in sexual assaults using DNA fragment analysis

During the investigation of sexual abuse, it is not rare that mixed genetic material from two or more persons is detected. In such cases, successful profiling can be achieved using DNA fragment analysis, resulting in individual genetic profiles of offenders and their victims. This has led to an increase in the percentage of identified perpetrators of sexual offenses. The classic and modified genetic models used, allowed us to refine and implement appropriate extraction, polymerase chain reaction and electrophoretic procedures with individual assessment and approach to conducting research. Testing mixed biological traces using DNA fragment analysis appears to be the only opportunity for identifying perpetrators in gang rapes.

Comparison between prostate specific antigen and acid phosphatase for detection of semen in vaginal swabs from raped women

OBJECTIVE

To compare the effectiveness of the prostate specific antigen (PSA) test and the acid phosphatase (AP) test for semen detection in human vaginal samples.

MATERIAL AND METHOD

The source materials were vaginal swabs that were tested at Ramathibodi Hospital between 2008 and 2010 from 2450 cases of raped women. Each swab was tested for semen by three methods: sperm detection by light microscopy, the AP enzymatic reaction, and the presence of PSA by using an immuno-chromatographic rapid kit test. The efficiencies of the AP and PSA tests were compared using the light microscopy result for the presence of sperm as the gold standard.

RESULT

The specificities of the AP, the PSA and the combined AP-PSA tests were 96.4%, 92.3% and 91.9%, respectively, and the sensitivities were 65.5%, 80.4% and 84.5%, respectively. The receiver operating characteristic (ROC) area of the AP, PSA and combined AP-PSA tests were 0.8091, 0.8639 and 0.8823, respectively. The ROC area of the PSA test was significantly greater than that of the AP test (p < 0.0001), and the ROC area of the combined AP-PSA test was significantly greater than both the tests individually (p < 0.0001).

DISCUSSION

Based on the ROC area, the PSA test was better than the AP test for semen detection in the vaginal swabs, and the combined results (AP + PSA) were better than the individual tests. The specificity of the AP test was higher than the PSA test in this study because a positive detection was made within only 15 s. While the PSA test was more convenient as it was available in a rapid test kit format, our recommendation is PSA detection should be done together with AP test and spermatozoa examination to identify evidence of rape.

CONCLUSION

Using these three tests together (AP, PSA, and spermatozoa detection) was recommended as a forensic tool for investigations of vaginal swabs of the rape victims.

Persistence of spermatozoa on decomposing human skin: a scanning electron microscopy study

Finding spermatozoa is of the utmost importance in judicial cases involving both the living and the dead; however, most of literature actually deals with inner genitalia and does not take into consideration the chance of external deposition of semen on skin, which is not rare. In addition, the most advanced microscopic technologies such as scanning electron microscopy (SEM) have not been thoroughly investigated within this specific field of research. This study aims at applying SEM analysis to samples of decomposed skin in order to test its potential in detecting spermatozoa particularly in decomposed cadavers. A sample of skin was obtained at autopsy and divided into two thin strips; one of the samples was used as a negative control. Semen was then taken from a "donor" (with a normal spermiogram) and was spread onto the other skin sample. Every 3 days for the first 15 days (for a total of six samples), a standard slide was prepared from swabs on the treated and control skin and analyzed by standard light microscopy. In addition, every 7 days up to 91 days (3 months circa), a skin sample was taken from the positive and negative control and examined by SEM for a total of 14 samples. Results show that after 12 days, light microscopy failed in detecting spermatozoa, whereas they were still visible up to 84 days by SEM analysis. This study therefore suggests the persistence of sperm structures in time and in decomposing material as well as the possible application of SEM technology to decomposed skin in order to detect semen.

Demonstration of DSI-semen--A novel DNA methylation-based forensic semen identification assay

Determining whether the source tissue of biological material is semen is important in confirming sexual assaults, which account for a considerable percentage of crime cases. The gold standard for confirming the presence of semen is microscopic identification of sperm cells, however, this method is labor intensive and operator-dependent. Protein-based immunologic assays, such as PSA, are highly sensitive and relatively fast, but suffer from low specificity in some situations. In addition, proteins are less stable than DNA under most environmental insults. Recently, forensic tissue identification advanced with the development of several approaches based on mRNA and miRNA for identification of various body fluids. Herein is described DNA source identifier (DSI)-semen, a DNA-based assay that determines whether the source tissue of a sample is semen based on detection of semen-specific methylation patterns in five genomic loci. The assay is comprised of a simple single tube biochemical procedure, similar to DNA profiling, followed by automatic software analysis, yielding the identification (semen/non-semen) accompanied by a statistical confidence level. Three additional internal control loci are used to ascertain the reliability of the results. The assay, which aims to replace microscopic examination, can easily be integrated by forensic laboratories and is automatable. The kit was tested on 135 samples of semen, saliva, venous blood, menstrual blood, urine, and vaginal swabs and the identification of semen vs. non-semen was correct in all cases. In order to test the assay's applicability in "real-life" situations, 33 actual casework samples from the forensic biological lab of the Israeli police were analyzed, and the results were compared with microscopic examination performed by Israeli police personnel. There was complete concordance between both analyses except for one sample, in which the assay identified semen whereas no sperm was seen in the microscope. This sample likely represents true semen because sperm cells were detected from an adjacent sample from the same garment, therefore in this case the assay appears to be more sensitive than the microscopic examination. These results demonstrate that this assay is a bona fide confirmatory test for semen.