A comparison of methods used in the UK and Ireland for the extraction and detection of semen on swabs and cloth samples

Evaluation of indirect transfer mechanisms of semen under varying test conditions

There is limited data available on the subject of indirect transfer of non-visible body fluids, particularly semen, and often forensic science practitioner experience alone must be used to guide expectations. It can be difficult to assess the likelihood of proposed transfer scenarios without knowledge of how different variables can affect a transfer. The following work carried out by the Association of Forensic Service Providers UK and Ireland Body Fluid Forum explores how the features of transferred semen change with differences in the primary and secondary surface (porous and non- porous), different contact types (passive, pressure and pressure+) and with wet and dry primary stains. It was concluded that the primary surface type and whether the stain was wet or dry when contact occurred had the most significant effect on the transfer of semen, with wet transfers and transfers from the tested non-porous surface producing significantly more, and larger, visible stains under white light, stains with stronger fluorescence as viewed using Crime-lite® ML2, stains with stronger and faster acid phosphatase reactions and greater numbers of spermatozoa viewed using high power microscopy, compared to dry transfers and transfers from the tested porous surface. Pressure with movement transfers resulted in significantly more visible stains under white light and greater numbers of spermatozoa viewed using high power microscopy compared to passive transfers, however this only occurred when transfers were from a porous primary surface. The secondary surface type was not found to have a significant effect on the numbers of spermatozoa viewed using high power microscopy.

Assessing the background levels of body fluids on hands

Forensic scientists are often asked to assist the court by evaluating the significance of finding body fluids on the hands of an individual; however, there is an absence of published data regarding the background levels of body fluids on hands. Whilst the scientist can use casework experience to inform the courts on the significance of the results, it would be advantageous to have data which could assist with this interpretation. This study was designed to ascertain the background levels of blood, semen, saliva, hairs/fibres and staining/debris on hands in the general population by sampling from delegates attending a scientific conference. The findings suggest that approximately one third of the population would be expected to have hairs or fibres on their hands and that females are more likely to have visible staining on their hands than males. Presumptive tests for blood and semen yielded negative results in all samples; however, almost 2 % of the samples were found to contain a very low number of sperm heads. In contrast, the majority of samples tested positive for the presence of saliva using the presumptive Phadebas® amylase test. The data supports the caution applied by forensic practitioners when evaluating the presence of saliva detected using the presumptive Phadebas® amylase test based on the lack of specificity and indicates that the RSID™-Saliva test would be more suitable to use.

The relevance of false positive acid phosphatase reactions indicative of the presence of seminal fluid from oral and vaginal samples

The Body Fluid Forum of the Association of Forensic Science Providers recognised concerns raised by forensic practitioners regarding the lack of data to inform on the incidence of significant AP (Acid Phosphatase) reactions from vaginal and oral samples, i.e. those which might be misinterpreted as indicating the presence of semen. This is particularly relevant in the light of appeal court rulings regarding the need for data to support evaluations. This paper presents collaborative data on the nature and incidence of AP reactions from vaginal and oral swabs provided by donors. The results demonstrate that caution is required with mid to strong purple AP reactions from direct testing of oral swabs and with mid purple reactions from vaginal swabs. The use of a Bayesian approach to assist with the provision of opinions regarding the presence of seminal fluid is highlighted.

Illuminating the benefits and limitations of forensic light sources

Forensic light sources, such as a Crime-lite, are used in forensic laboratories and by police staff in the examination for, and detection of, biological material. Whilst the benefits of using forensic light sources are relatively well understood, their limitations are less-so. This report details the outcome of studies, validation and review by three forensic laboratories, as well as three case examples, to highlight both the strengths and weaknesses of the tested forensic light sources and to demonstrate that, whilst a useful preliminary screening tool, they should not be used in isolation without subsequent presumptive chemical testing. False positives and negatives are common, and the background substrate and specific biological material present can have a significant effect on the outcome of examination when using a forensic light source.

Persistence of Semen on five different fabric types in various water environments

Evidence collected from biological fluids obtained from a crime scene is essentially important in forensic cases. A potential profile can be generated from these obtained samples and this can help in identifying the victims and/or suspects of sexual assault. The water environments selected for this study are all related to the potential crime scenes from which there is a possibility of finding a dead body or clothing of a sexual assault victim. Tap water, River water, Swimming pool water, and Canal water were selected. Fabric types selected were khaddar, linen, silk, polyester, and chiffon. Detection of seminal stains was carried out by three methods; Alternate Light Source (ALS), Acid phosphatase (AP) testing, and Kernechtrot-Picro-indigo-carmine (KPIC) testing. These tests were performed for each fabric type in each water environment after regular intervals, 24 h, 48 h, 72 h, 4 days, 7 days, and 14 days. This study aimed to compare the ability of five types of fabrics to retain seminal material after immersion in four different types of water environments. Fluorescence was only detected in tap water-soaked silk fabric after 14 days of immersion. Seminal fluid was detected in khaddar, chiffon, silk, and polyester in samples immersed for 14 days in tap water. Spermatozoa were retained by khaddar and silk immersed in tap water, Polyester fabric in tap and river water, Chiffon in only river water and Linen in swimming pool water when immersed for 14 days. However, fluorescence, seminal fluid or spermatozoa were not detected in linen fabric regardless of all the afore mentioned variables.

Generating aptamers towards human sperm cells using massively parallel sequencing

Determining the presence of sperm cells on an item or swab is often a crucial component of sexual offence investigation. However, traditional histological staining techniques used for the morphological identification of spermatozoa lack both specificity and sensitivity, making analysis a complex and time-consuming process. New methods for the detection of sperm cells based on aptamer recognition may be able to overcome these issues. In this work, we present the selection of ssDNA aptamers against human sperm cells using Cell-SELEX and massively parallel sequencing technologies. A total of 14 rounds of selection were performed following a modified Cell-SELEX protocol, which included additional steps for the isolation of spermatozoa from seminal fluid. Massively parallel sequencing using the Illumina Miseq platform was conducted on enriched aptamer pools to elucidate the structure of potential binders. A custom bioinformatics pipeline was also developed using Galaxy for the automated processing of sequencing datasets. This data revealed several promising aptamer candidates, which were shown to selectively bind sperm cells through both microscale thermophoresis and enzyme-linked oligonucleotide assays. These aptamers have the potential to increase the efficiency of sexual offence casework by facilitating sperm detection.

The development of a rapid and reliable method (SAPSWash): For the extraction and recovery of spermatozoa from superabsorbent polymer containing products

This work presents a rapid and reliable method to recover spermatozoa from Super Absorbent Polymers (SAPs) commonly found in sanitary protection products such as nappies and sanitary towels. The use of salt solutions was investigated and a protocol was developed using a calcium chloride (CaCl₂) solution to release semen deposited onto a selected SAP containing product. The method was tested on ultra-sanitary towel samples treated with a known amount of semen. A range of treatments were examined; some samples were prepared and immediately frozen for storage and others were allowed to air dry overnight to replicate the condition of similar items recovered for examination in sexual offence cases. The method allowed the collection of low yields of spermatozoa, but these were still sufficient for microscopic identification of intact heads and to obtain ESI17 DNA profiles from all the samples. This report presents the method, the results obtained and discusses prospective adaptations to the method for validation to implement the method into forensic casework.

Species identification of semen stains by ATR-FTIR spectroscopy

Semen stains are the most important biological evidence when identifying the aggressor in sexual assault cases. Current detecting assays of semen stains species identification were not confirmative enough. In this study, we investigated the potential of species identification of semen stains by using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy combined with advanced chemometrics methods. The effect of substrates types and time since deposition (TSD) were considered in the study. A partial least squares-discriminant analysis (PLS-DA) classification model was established which demonstrated complete separation between human and other species (rabbit, dog, boar, bull, and ram). Validation was conducted which showed prediction abilities with 100% accuracy. Additionally, we found species identification could be achieved without sperm cells which proved ability of spectroscopic methods detecting the semen samples from the case of azoospermia. This work provides a powerful and practical tool for species identification of semen stains in real forensic casework.

The evaluation of Oryza sativa L (Black rice) extracts for detection of spermatozoa on the clothing and vaginal swab samples

Investigation of sexual assault cases from the evidence involving vaginal swab, clothing and others is examined by a forensic scientist. The explanation of trace findings on spermatozoa on clothing is often problematic due to the use of different staining methods. Conventional staining method used either Papanicolaou (PAP) or Dip quick® stain as synthetic dyes which are expensive imported material and harmful to human health. Therefore, the present study aims to determine the ability of Oryza sativa L (black rice) extract as a natural dye to detect spermatozoa on the clothing and vaginal swab casework samples for routine forensic examination. Results revealed that black rice extract has a highly effective for detecting spermatozoa on cloth and vaginal swab casework samples. There was no significantly different in the detection of spermatozoa compared with rapid PAP stain and Dip quick® stain. Results also showed that the staining of vaginal swab casework with black rice extracted can be used for PCR amplification of centromeric alphoid repeat gene on chromosome Y for 60 days. Moreover, the DNA extracted from stained semen slide generates a full profile of 16 alleles of STR typing. The results indicate that a new natural staining dye which extracted from black rice can be used to detect spermatozoa and identify a person from the trace evidence. The application of natural dyes for routine staining of spermatozoa from forensic specimens will decrease the expense to be spent in purchasing the synthetic dye and reduce their side effects on human and environment.

Biological Evidence Management for DNA Analysis in Cases of Sexual Assault

Biological evidence with forensic interest may be found in several cases of assault, being particularly relevant if sexually related. Sexual assault cases are characterized by low rates of disclosure, reporting, prosecution, and conviction. Biological evidence is sometimes the only way to prove the occurrence of sexual contact and to identify the perpetrator. The major focus of this review is to propose practical approaches and guidelines to help health, forensic, and law enforcement professionals to deal with biological evidence for DNA analysis. Attention should be devoted to avoiding contamination, degradation, and loss of biological evidence, as well as respecting specific measures to properly handle evidence (i.e., selection, collection, packing, sealing, labeling, storage, preservation, transport, and guarantee of the chain custody). Biological evidence must be carefully managed since the relevance of any finding in Forensic Genetics is determined, in the first instance, by the integrity and quantity of the samples submitted for analysis.

The effect of mark enhancement techniques on the subsequent detection of semen/spermatozoa

Fingermarks, footwear marks, blood and semen are amongst the most commonly encountered types of evidence at crime scenes. Previous work has extensively investigated fingermark and blood enhancement techniques and a sequence developed to maximise evidence recovery; however, there is limited research as to the effect of these techniques on the subsequent detection of body fluids such as semen. In this study, seven fingermark and blood enhancement techniques (e.g. powder suspension, cyanoacrylate fuming and acid violet 17) were employed followed by the subsequent detection of semen/spermatozoa. Other variables included in the study were the use of two substrates (white ceramic tiles and grey laminate flooring), a depletion series and ageing periods of 1, 7, 14 and 28 days. The effect these techniques had on the subsequent detection of semen was assessed by visual and fluorescence examination followed by presumptive and confirmatory testing for semen and spermatozoa. The results found that protein stains (acid violet 17 and acid yellow 7) caused a loss in presumptive test reactivity; however, sperm heads were still observed using microscopic examination after extraction and staining. The use of black magnetic powder, Bluestar(®) Forensic Magnum luminol, Lumicyano™ 4% and cyanoacrylate fuming followed by basic yellow 40 staining did not hinder subsequent presumptive and confirmatory tests for semen and sperm heads. Powder suspension caused a loss in both presumptive test reactivity and sperm heads from the substrate. In general, the enhancement techniques resulted in the improved visualisation of the semen stains under white and violet/blue light. The results from this study aim to provide a strategy to maximise evidence recovery and improve efficiency in an integrated forensic approach.

The recovery of semen from bathwater using the Evidence Recovery System (ERS)

Sexual offences are under-reported and ascertaining accurate offence numbers is difficult. Any methods which could increase the ability to obtain biological evidence or reduce the additional distress associated with reporting a sexual offence may result in an increase in reporting this crime type. The Evidence Recovery System (ERS) is designed to collect trace evidence, including hairs, fibres and biological evidence, from bath or shower water in a non-invasive manner. Initially, samples of semen were placed in baths filled with water, and washing was simulated using a range of body wash products. The water was then drained through the ERS before its filters were subjected to acid phosphatase testing and haematoxylin and eosin staining of spermatozoa. Recovered spermatozoa were then graded accordingly. Following this, the experiment was repeated with the addition of dirt/dust particulates during the washing stage, to simulate recovery of biological evidence in a more realistic environment. The results showed that spermatozoa considered 'easy to find' could regularly be obtained from bathwater using the ERS. It appeared that this recovery was not affected by the presence of different body wash products. When dust/dirt particles were added, the number of spermatozoa recovered increased at two of the evidence collection stages. The difference in recovery was considered to be statistically significant. This study provides evidence to suggest the feasibility of use of the ERS as a method to collect semen evidence from individuals subjected to sexual offences. The recovery of spermatozoa does not appear to be affected by the presence of a body wash, but does appear to be improved when skin cells, hair and other debris are transferred into the water, as would be likely during a bath/shower. Further to this, the possibility of obtaining spermatozoa from the home bath or shower of a victim following a post-offence bathing experience is implied.

Optimisation of choline testing using Florence Iodine reagent, including comparative sensitivity and specificity with PSA and AP tests

The detection of semen in forensic science is essential in cases of sexual assault but can be problematic in the absence of spermatozoa. Choline is known to occur in high concentrations in seminal fluid and the Florence Iodine test for its detection has been used in forensic science for many years, however very little is documented regarding its sensitivity and specificity in forensic casework. This paper describes the optimisation of the choline Florence Iodine test (FI) and investigates the sensitivity and specificity of the test against different body fluids, food and drink substances, cleaning products and laboratory chemicals. Comparative testing against Acid Phosphatase (AP) and Prostate Specific Antigen (PSA Seratec®) tests is described and shows that the FI test has greater specificity than the PSA test which cross reacts with a number of body fluids.

The forensic aspects of sexual violence

Complainants of sexual assault may disclose to different agencies, the police and health professionals being the most likely. It is possible for certain evidence types to be collected before a clinical forensic assessment takes place that do not require the need for a Forensic Medical Practitioner. If the time frames after the incident and the nature of assault warrant the need for a forensic medical examination of either a complainant or a suspect, this should only be conducted by doctors and nurses who have received relevant, up-to-date specialist theoretical and practical training. Clear evidence shows that few other criminal offences require as extensive an examination and collection of forensic evidence as that of a sexual assault. The forensic evidence in a case may identify an assailant, eliminate a nominated suspect(s), and assist in the prosecution of a case. The elements of forensic medical examination, reviewed in this chapter, are those that are the most varied across jurisdictions around the world currently. Key focus points of this chapter are considerations for early evidence collection, utilising dedicated medical examination facilities for sample collection, contamination issues associated with evidence collection and certain practical aspects of forensic sampling methods which have evolved given results identified by Forensic Scientists processing evidential samples in sexual assault cases, Some of the problems encountered by the forensic science provider will also be discussed.