Speeding Up Sexual Assault Investigations with Chemistry

Speeding Up Sexual Assault Investigations with Chemistry

A recent study has demonstrated a new technique for the rapid detection of semen and the chemical differentiation of condoms, offering a new potential tool to assist sexual assault investigations.

Hundreds of thousands of cases of sexual assault and rape are reported each year, though this is undoubtedly a fraction of the actual number. The successful identification and prosecution of offenders in sexual assault cases often hinges on the ability to detect and collect biological fluids such as semen, essential for supporting victim statements and identifying the offender. In the past, the identification of semen has relied on destructive, non-specific presumptive tests, often based on a colour change reaction in the presence of a specific chemical in semen. In recent years, there has been a push for the development of preparation-free analytical techniques that could be used for the analysis of sexual assault evidence at crime scenes or in hospitals.

In a recent study published in Forensic Chemistry, a method using ambient ionisation mass spectrometry has been developed for the analysis of sexual assault evidence, specifically semen and condoms. Ambient ionisation MS refers to a type of mass spectrometry which allows the rapid, direct analysis of a material, eliminating the need for the time-consuming and destructive sample preparation steps that limit traditional techniques.

This particular technique, called sheath-flow probe electrospray ionisation MS, uses a small, cheap-to-construct probe that is simply touched to the surface of the sample. The probe is then placed in front of a mass spectrometer inlet and a voltage applied to produce an instant unique chemical profile. In all, a sample can be analysed in a matter of seconds.

In this study, semen was successfully detected on various materials, such as fabric and condoms, mimicking the kind of environments the body fluid could be encountered during a sexual assault investigation and, crucially, showing the ability of the technique to work with different surfaces. Whereas presumptive tests for semen are focused on the presence of one chemical, making them prone to “false positives”, this new technique harnesses a suite of chemicals, allowing a more confident identification of semen. It was also shown that semen could still be detected after 40 days of ageing. This is important as during a criminal investigation it may be days, weeks or even longer before evidence is seized and analysed. After 40 days, the chemical profile was remarkably unchanged, indicating that even older semen could potentially be identified.

The study then took this technique one step further, applying it to the analysis of condoms. As criminals become more knowledgeable about forensic evidence such as DNA, there has been an increase in the use of condoms by criminals to protect their identity. By analysing the surface of different brands and types of condom, it was demonstrated that unique chemical profiles were associated with the different condoms, with notable chemicals relating to the condom’s material or flavouring being detected. This has two major implications. Firstly, the ability to detect lubricants and traces from condoms could prove beneficial in confirming condom use, particularly important when biological evidence is lacking. Furthermore, the unique chemical profiles could even open up the possibility of indicating what type of condom was used by the offender, offering more information to the investigation.

Direct analysis techniques such as this have great potential to speed up forensic investigations, but it will no doubt be years before such technology is considered for adoption by police forces.


Rankin-Turner et al. Using mass spectrometry to transform the assessment of sexual assault evidence. Forensic Chemistry, 2020, DOI: 10.1016/j.forc.2020.100262

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Fingerprint Technology to Prevent Pangolin Poaching

Fingerprint Technology to Prevent Pangolin Poaching

Pangolins are amongst the most illegally trafficked mammals in the world, with hundreds of thousands being slaughtered each year for their meat and scales. In recent months, pangolins have gained extra attention due to their link to the spread of COVID-19, resulting in the Chinese government making efforts to control the use of pangolin scales in traditional medicine. All eight species of pangolin are protected and included on the International Union for Conservation of Nature’s Red List of threatened species, but this does not deter criminals from capturing and selling these animals.

In recent years forensic techniques have been harnessed in the fight against poaching and illegal animal trafficking, in particular with the aim of linking illegally traded animal materials to the perpetrator. Materials derived from animals pose a particular challenge for traditional fingerprinting techniques, with techniques often not being suitable for use on the likes of scales, feathers and skins of animals. Furthermore, in order for fingerprint development and collection techniques to be rolled out across relevant countries, the tools developed need to be easy to use, effective and inexpensive.

In a recent study published in Forensic Science International, a team of researchers at the University of Portsmouth developed a technique for lifting fingermarks from the scales of pangolins, demonstrating the potential to connect criminals to illegally traded pangolins via fingerprints. As an individual pulls scales from a pangolin, it is likely that fingermarks will be deposited on the scales. However, determining the best development technique for this unique material can be challenging.

The technique presented employs lifters which contain a soft gelatine material ideal for picking up traces and impressions when pressed against a surface. Low-adhesive gelatine lifters have been used in forensic practice for decades, particularly for lifting footwear marks and fingermarks off objects, but have not been widely applied in wildlife crime. The surface of a pangolin scale is uneven, containing voids that could be problematic for some development techniques. However, the soft nature of the gelatine allows the lifters to press into the voids and lift as much material as possible.

In this study, scales from varying African species of pangolin were provided by the UK Border Force for the assessment of the gelatine lifting technique. Of the marks lifted from pangolin scales, 74% exhibited ridge detail and 24% showed no ridge detail but evidence of contact. Once lifted, the fingermarks could then be imaged using a camera or mobile phone camera for rapid digitisation. Although only a pilot study, the research has demonstrated that the gelatine lifter could be easily applied to the scales of the pangolin and subsequently preserved for scanning and comparison, providing law enforcement with a potential route to identify poachers.


Moorat et al. The visualisation of fingermarks on Pangolin scales using gelatine lifters. Forensic Science International, 2020. DOI: 10.1016/j.forsciint.2020.110221