The initial report and early evidence considerations

The first appropriately trained person to encounter the complainant may need to collect certain types of early evidence. These samples may include sanitary wear, urine for toxicology, samples from the oral cavity where oral sex may have been alleged, hand and fingernail samples and non-intimate skin samples. The decision to collect these samples is based on immediate medical needs, the welfare of the patient, availability of a Forensic Medical Practitioner (FMP), or delays in reaching a dedicated forensic examination facility.

One of the first dedicated early evidence kits was developed by the Forensic Science Service ^® together with the Metropolitan Police in 2001. The practical nature of the kit was highlighted as good practice by a ‘Her Majesty’s Inspector of Constabulary’ and ‘Crown Prosecution Service ‘ report on the joint inspection into the investigation and prosecution of cases involving allegations of rape, published in April 2002. Evidence indicates that the concept of early evidence kits is now more readily available to front-line officers and Accident and Emergency Departments in many jurisdictions. As a backup to having kits readily available at exam sites or with examiner programmers, jurisdictions may also want to consider the feasibility of storing a few kits in police patrol cars. Variations in temperature, however, even within one jurisdiction must be born in mind, as heat exposure could affect kit contents before use. It is important that, before an encounter with the woman, an FMP establishes whether any of these samples have already been collected and by whom.

Practically, clothing worn by the complainant at the time of an alleged assault is normally seized with their permission, as it may provide useful forensic evidence for contact traces; equally, it may provide important points of reference for the FMP in relation to injuries (e.g. where the clothing is damaged). It is common practice for this clothing to be seized before the FMP examines the complainant. It is good practice for the FMP at the point of call-out to establish if the complainant has presented in the original clothing and if damage or injury has occurred. It is advisable in such situations to ask for the woman to remain in the clothing until the FMP has assessed them. It is acknowledged that, if serious injury has occurred, the clothing may have to be cut to facilitate its removal. Any pre-existing damage should be avoided being cut through as it makes it impossible for the FSP to assess the damage in relation to the nature of the assault. It is good practice for the FMP to liaise with the emergency team if clothing has to be removed. Record photography of clothing positions and the extent of any damage before removal are considered useful, as it shows fashion trends and the style of the wearer. As an example, it is difficult to assess damage positions with hosiery once the garment is off the body. Who should take the photo documentation is under debate, but it may be relevant for the forensic scientist to view video or photographic material recorded by the FMP in relation to clothing damage, injury, body mapping in relation to contact traces and body fluid recovery.

Evidence-based sampling time frames

A number of practical guidelines are available to assist the FMP in deciding whether a forensic medical examination of complainant or suspect should be conducted immediately or deferred. This is particularly important, as many complainants of sexual assault will report during out-of-office hours. The FMP should speak directly with a police officer investigating the allegation about time frames and points to prove. Further considerations include post-offence activity of the woman. Local advice may be to speak directly with the FSP about what should be seized according to the crime report.

Evidence-based sampling time frames

A number of practical guidelines are available to assist the FMP in deciding whether a forensic medical examination of complainant or suspect should be conducted immediately or deferred. This is particularly important, as many complainants of sexual assault will report during out-of-office hours. The FMP should speak directly with a police officer investigating the allegation about time frames and points to prove. Further considerations include post-offence activity of the woman. Local advice may be to speak directly with the FSP about what should be seized according to the crime report.

Contamination issues

Contamination is a crucial issue for everybody involved in the collection of forensic evidence during a sexual assault investigation to be aware of. It is particularly important where the FSP is concerned with the analysis and interpretation of trace DNA. From a theoretical perspective, the forensic scientist considers any DNA deposit identified that is not immediately relevant to the crime being investigated as potential contamination. Reported evidence shows that contamination has occurred in a number of different ways: (1) before the sexual assault being committed ; (2) in the interval between the crime and a forensic medical examination taking place; (3) during the forensic medical examination ; and (4) within the forensic science provider (FSP) laboratory. Although points (2) and (3) are considered as adventitious transfer and cannot be strictly controlled, the FMP should apply methods to minimise the effect of such contamination occurring. One example of good practice includes the provision of dedicated forensic medical examination kits containing disposable equipment and unopened controls. It is crucial that the consumables within the kits do not compromise the integrity of the samples collected or adversely affect the forensic analytical process in any way, and several studies have looked at this problem. The FMP’s use of disposable hospital scrubs when conducting an examination, changing gloves between examination of different body areas, logging all persons in the room at the time of the medical taking place, and staff providing elimination DNA samples can all minimise the occurrence of contamination.

Unsolved sexual assault investigations of today may well become the cold-case investigations of the future; as such, potential forensic evidence must be correctly collected, stored and examined with trace DNA detection sensitivities in mind. Any deviations from locally recommended protocols must be documented, with clear justifications recorded ( Table 1 ).

The forensic medical examination facility

Many jurisdictions now have specially designed dedicated examination facilities for the examination of complainants of sexual offenses. These have fixtures and fittings that are durable with washable surfaces, and can be cleaned between forensic examinations. Practically, it is important to monitor equipment and examination areas to identify if any significant levels of DNA are present, and subsequently whether cross-contamination between cases could be considered a possibility. Evidence has shown that the provision of an environmental monitoring process helps focus how successfully the cleaning procedures are implemented within the facility and identifies any problem areas. Comparison of DNA results obtained from the environmental samples with all relevant staff profiles could also identify any gross contamination seen.

Unfortunately, the examination of potential suspects in sexual assault investigations is much more ad hoc, and little information has been recorded on this. Often detainees are forensically examined in cramped medical rooms that are not for dedicated forensic use. Few jurisdictions have dedicated forensic cells. The use of ‘dry’ cells with no provision of toilet or hand-washing facilities within the cell for the detainee to use to remove potential forensic evidence are the defaultable option in many jurisdictions. No studies were found for the recommended standards for forensic facilities available for the examination of suspects in sexual assault investigations.

Other issues to consider in reducing cross-contamination include the importance of having examination facilities with a suitable area or at least a non-cluttered wall surface if record photography is required. This includes the ability for total black out where ultraviolet photography is used.

The role of the forensic science provider

Forensic evidence is essential in any sexual assault investigation because it can identify a suspect or a crime scene, or provide corroborative evidence about what sexual acts have occurred. It may also identify possible series links or demonstrate repeat offending by the same suspect. Semen found on intimate swabs may have a more probative value than semen found on clothing or bedding, because it only has a finite time for survival compared with dried drainage on fabrics. If a sexual assault involves oral, digital or foreign object penetration, then it is useful for the FSP to be provided with as much detail as possible about the alleged offence to process the evidence most effectively. Therefore, in order to maximise all forensic opportunities and to plan the order of analysis, it is important that the police investigator discusses a forensic strategy with the FMP to ensure relevant forensic evidence is secured at an early stage. Good evidence shows that this occurs when dealing with complainants but is less likely for nominated suspects.

Given that the accused suspect will often allege that the complainant has consented to the sexual act, forensic evidence in such cases is more problematic and often requires examination of a large number of exhibits looking at discrepancies between the accounts of those involved. In cases where the complainant is known to the suspect, forensic results have to be interpreted carefully, as legitimate contact could account for some of the findings.

In recent years, in many jurisdictions, victims of sexual assault often report an unclear recollection of what has happened to them. These reports are usually associated with alcohol drug consumption, or both. In many cases, the complainant alleges interference with their drink. The FSP has a dual role here to establish whether sexual activity took place and to conduct toxicology analysis to check for drug or alcohol consumption.

Forensic sample site identification

Trace DNA analysis has become an integral part of an FSP’s workload in relation to sexual assault investigation. DNA methodologies based on polymerase chain reaction have allowed the generation of profiles in sexual assault cases in recent years that were not previously examined. This, in turn, has lead to the success of many national offender DNA databases.

When dealing with trace samples from complainants or suspects of sexual assault, it is important to identify which areas to target. By their very nature, such trace samples are not readily obvious. Swabbing an assumed trace sample area that is smaller than the actual deposition area could mean that some of the relevant sample goes uncollected. Alternatively, sampling a much larger area than that of the actual deposit may mean that the sample is spread over a larger surface area and that overall less sample is collected or becomes diluted. Both practical approaches have the potential to give an inaccurate view of where the actual sample was located. The uses of non-invasive detection systems are helpful here and, as such, the Polilight is used to initially examine the patient in a number of jurisdictions. Numerous studies have shown the value of speculative searching scene items and articles of clothing with a Polilight equivalent. Forensic odontologists use ultraviolet photography to document bite marks on skin as the light penetrates the epidermis or upper levels of the skin down to a few hundred microns in depth, which helps to focus on the surface damage while minimising the appearance of visible bruising. Studies looking at traditional photography have shown that these standard methods may interfere with the viewing and characteristics of the injury.

Some studies indicate that ultraviolet light may cause semen and saliva to fluoresce. Other studies contradict this. For example, Santucci et al. identified many creams and ointments that fluoresced on exposure to a Woods lamp (wavelength 360 nm), which is used in a number of countries when examining women who have been sexually assaulted; however, none of the semen samples examined by Santucci et al. fluoresced. Other research has shown that ultlraviolet light provides non-ideal results in the examination of women, as many traces accounted in day-to-day situations also fluoresce (i.e. detergents and lubricants that contain petroleum jelly and milk). It is possible at higher intensity light sources using goggles to detect semen even when the background surface is also fluorescent, but the perceived impracticality of this method does not make it ideal. Nelson and Santucci in their study asked FMPs in training to use an alternate light source, the Bluemaxx BM 500, as it gives 100% sensitivity, and to differentiate it from other trace substances. It must be remembered that some fibres may also be visible under ultraviolet light, which enables the FMP to visualise these for collection on skin and within hair. If the FMP is not a regular user of light sources as a means to identify potential contact traces, this does create a practical problem in identifying relevant areas of luminescence, This, however, may be overcome by conducting controlled photographic trials that show different body fluid deposits (including mixtures), commonly applied skin products, and lubricants (e.g. on different skin types), and creating a reference book of standards available for review in the medical examination facility (Miller A, Product Manager at Forensics Source, Jacksonville, Florida, USA, April 2012, personal communication).

In general terms, forensic photography using normal lighting conditions is an important element of a forensic medical examination. Internationally, variation exists on the extent of forensic photography necessary, including when colposcopy of intimate areas is used. Some jurisdictions routinely take photographs of both detected injuries on patients and normal (apparently uninjured) anatomy, whereas others limit photography to detected injuries. It must be born in mind that the photographs may also help the forensic scientist with their interpretation of findings and, as such, should be made available to them where appropriate. A photographic record of a woman who presents soon after a sexual assault still wearing the same clothing is considered useful if the woman agrees.

Pre-printed body diagrams and maps are also useful for recording any injuries and should be used by the FMPs in their assessment of a patient, in addition to the use of photography. It may be beneficial for these records to be forwarded to the FSP to assist in their forensic assessment of any contact traces on the clothing worn at the time of the assault. This is particularly useful when there has been a long delay between the sexual assault and the medical examination taking place, particularly when the complainant has washed in the intervening time.

The forensic medical examination kit

Sexual assault evidence collection kits vary between countries and even between jurisdictions of the same country, so it is not possible within the scope of this chapter to discuss the variations. What is important is that the kit, or its modules, are periodically reviewed for efficiency and usefulness on the basis of evidence-based findings obtained from the FSPs, and any changes are made as needed. In the UK, the Faculty of Forensic and Legal Medicine have a scientific committee that includes FMPs, FSPs, police investigators and forensic kit manufacturers that meet biannually to discuss the content of forensic kits used to sample complainants and suspects of sexual assault. A sampling recommendation document is produced for faculty members after the meetings have taken place with any changes highlighted within it. In addition to kit content reviews, it is important to establish mechanisms to ensure that kits at exam facilities are kept up to date (e.g. if a new evidence collection procedure is added, facilities need to know what additional supplies should be readily available to FMPs).

Variation also exists in who covers the cost of a forensic medical examination; in some jurisdictions, it can be down to the individual themselves, particularly where the complainant does not wish to involve the criminal justice agency at the outset and as such provide anomalised samples. Elsewhere, the cost of the medical examination and the forensic analysis of the samples is paid for by the local criminal justice agency regardless of whether the police are involved or not. It is not uncommon for a restricted forensic budget to be made available where anomalised reporting applies. Training and policies should actively discourage decision making about evidence collection that is based on extraneous factors, such as reluctance of a criminal justice agency to pay for sexual assault evidence collection or subsequent forensic analysis.

Collection of forensic samples

For forensic sampling from a patient, complainant or suspect of sexual assault, most trace samples are collected using swabs. Some jurisdictions use the medical forensic history, the examination, and patients’ consent to determine whether and where to collect swabs, whereas others collect swabs from all orifices and from the surface of the body (with patients’ consent). In particular, some do not collect anal swabs unless indicated.

The swabs and containers differ from those used for clinical purposes. Other methods have also been used practically to recover evidence. These have included the use of surgical gauze pads. The swabs should be made of fibres that readily release the collected absorbed material during extraction. In recent years, considerable research has been undertaken into fibre compositions and whether this makes a difference to the amount of collected material subsequently released. Recently, other swab types, such as foam, flock and Dacron, have been introduced. The collection device used for recovery of trace DNA is often a matter of convenience i.e what has always traditionally been used, often based on old research in relation to evidence recovery and the price of the device, rather than what is fit for purpose given more recent research on recovery and findings.

Swabbing of a non-genital skin area that is dry has always required moistening of the swab to traverse the sampling area a number of times. Limited pressure is applied to prevent exfoliation of the patient’s own epithelial cells, while rotating the swab so that the whole surface area can be included in maximising the collection process. Research has shown that use of a single moist cotton swab may not pick up all the available material from the surface, and it has been shown that this technique may only remove half of the available material from the sample site. Few FSPs have undertaken research studies to check the composition of the swab head and whether the swabs being used in forensic medical examination kits are better or worse than alternatives now available on the market. Further research into optimal collection methods and swab types would be beneficial given the tiny amounts of trace evidence recovered in sexual assault investigations.

Skin sampling

Trace DNA is a term used by many to describe minute quantities of DNA transferred thorough skin contact. The small numbers of cells and the nature of the type of transfer make identification of the cellular source of origin (e.g. buccal and epithelial) impractical or impossible as discussed by Wickenheiser. The nature and the extent of the contact from licking, kissing or biting may result in salivary amylase also being transferred, which is the only means for the forensic scientist to identify the presence of the fluid as potentially being saliva. The traditional test used by many FSPs is still the Phadebas ^® amylase test. Specificity, however, is a problem, as amylase can be present in body fluids other than saliva.

It is now common practice to carry out a double-swabbing technique as advocated in the research by Sweet et al., who showed that it is possible to obtain a DNA profile from saliva stains (corresponding to a bite mark) on the skin of a cadaver where deposition had occurred up to 48 h earlier. This technique involves moistening the first swab and leaving the second swab dry. It could be argued that by keeping the second swab dry, if the first swab was successful in absorbing all the moisture it deposited onto the skin, then this second swab may not collect as much from the sample site as if it too was moistened before swabbing. It is important that any residues of water are recovered. Where multiple swabs are used, the FSPs look to co-extract the swabs in order to maximise or enhance DNA retrieval.

Water is still the moistening agent advocated for use by FMPs, but given that FSPs use other reagents to moisten swabs when retrieving trace DNA from inanimate items, this is an area of research that may highlight improved recovery. Currently, if the sexual assault involves an unknown assailant, and bite marks or injuries on the skin are present that can be attributed to direct contact by the assailant, then if the complainant has not showered or bathed, some recommendations suggest sampling the area up to 7 days after the incident. Control swabs should also be taken from an area adjacent to the site of sampling or the mirror image on the body so that the FSP has access to the level of background DNA at the time of sampling to aid interpretation when the presence of a body fluid or DNA in a specific area is significant. Research is still limited on the persistence of body fluids and cellular material on the skin with these problems in mind. Given that pubic hair is often completely shaved off for hygiene or ethical reasons by women being forensically examined, then logic suggests that if hair is not present, it is more likely for semen to drain and deposit onto the pubic skin or onto the skin of the inner thighs. These uncommon sample sites should be considered as a matter of routine sampling in such situations.

In addition, Minitapes are being used to lift potential cellular material from the skin in some jurisdictions, and recent reports have shown that this method is more effective than swabbing for the recovery of salivary DNA. Minitapes are small pieces of sterile adhesive clear tape on a plastic backing strip that can be pressed repeatedly onto the surface of skin to collect any loosely adhering cellular material.

Although the swabbing and taping techniques described above may seem logical and straightforward, inadequate training, combined with the absence of competency testing when an FMP first starts, and a lack of ongoing refresher training, could drastically limit the success rates of the samples collected. Consistent initial forensic training and regular forensic update training is, therefore, needed for FMPs.

Variation exists between jurisdictions about how collected swabs are stored and processed. The ability to properly collect, preserve and analyse the sample is important for preserving the integrity of potential forensic evidence. Stabilisation is a key part of the chain of evidence in sexual assault cases, as it is often biological evidence and DNA tests derived from them that the FSP is considering. Forensic testing of samples is generally not carried out immediately after collection. It is also not uncommon for retesting of stored DNA samples to occur with the advent of further requests as part of an investigation or where new technologies are introduced.

Limited research suggests that if biological material is allowed to dry on a swab before extraction, then less DNA is retrieved than if the still moist swab was processed immediately. In practical terms, this is because the forensic medical examination facility is not in the same location as the FSP laboratory so, in some jurisdictions, the collected swabs are stored frozen immediately after collection and kept frozen when being transported to the FSP. These storage methods are expensive because of the cost of electricity in a number of countries, the space taken up, and the possibility of breakdown. Research has shown that freezing swabs, rather than drying them before extraction results in DNA recovery rates approaching that of a tested moistened swab. Other numerous examples show that degradation occurs during storage, in the cold or at ambient conditions.

Cotton swabs, being made of a natural fibre, are more likely to go mouldy if left damp without drying or freezing the sample. As already mentioned, environmental temperatures, distances the forensic samples travel, and lack of freezer storage space at the FSPs are, therefore, problematic if cotton swabs are used. These issues have been considered in numerous jurisdictions in terms of fit for purpose swab type and packaging and storage methods. In South Africa, Dacron swabs are used for sampling body fluid traces, and the swabs are placed in triangular suspended boxes and air dried (Steyn P, Senior Technical Officer-Chemistry, University of Stellenbosh, South Africa, April 2012, personal communication). This means that a cold chain of evidence is not required. Dacron swabs are also used in Australia (Cooper J, ADF Investigative service Forensic Manager, Australia, April 2012, personal communication).

Some new research in the USA has looking at a storage medium SampleMatrix™, which is a polymer that protects the sample in storage at room temperature and that completely dissolves after rehydration. It suggests that this may be a method that in the future could be applied to sexual assault samples. Variation with sample storage methods, coupled with the associated problems mentioned, warrants further investigation by the forensic science community at an international level.