August 13, 2020 by Locard's Lab

Sex Determination Through the Chemical Analysis of Fingerprints

Fingerprints have been a staple of forensic science for decades, providing a reliable (though not perfect) means of identifying suspects and placing people at crime scenes. In recent years, scientists have turned their attention towards exploring the additional information that could be extracted from fingerprints, in particular, chemical information for police intelligence. Fingerprints are composed of a mixture of chemical compounds both excreted through our skin and picked up from the environment.

Over the past decade, analytical chemists have shown that there may be sufficient chemical differences in the fingerprints of male and female donors to differentiate between the sexes. By studying these chemical differences, it may be possible to build a model capable of predicting the sex of a fingerprint donor based on the chemical compounds within the fingerprint.

In a recent study published in Forensic Chemistry, a method was developed to predict the sex of a donor based on the presence of peptides and proteins in fingermarks. The study used MALDI-MS (Matrix-assisted laser desorption/ionization mass spectrometry), a type of mass spectrometry that enables both the measurement and identification of the chemical constituents in a material, in addition to the imaging of samples. MALDI has already been demonstrated to be a powerful technique in the chemical analysis of fingermarks, including imaging fingermarks and detecting the presence of blood and drugs in the mark. Much of the research in the area has been led by Professor Simona Francese of Sheffield Hallam University in the UK, senior author on this recent paper.

In the study, 199 participants donated multiple fingermarks, culminating in hundreds of samples for analysis. The fingermarks used for the analysis were natural, that is to say, deposited with no fingertip preparation beforehand. Many studies in the chemical analysis of fingerprints use “groomed” marks, in which the fingers are rubbed on the face or forehead in order to load the fingers with skin secretions prior to deposition. Although this provides rich samples for analysis, they are not applicable to fingermarks encountered in the real world.

After fingermark collection, MALDI-MS was then used to analyse the samples, focusing on the measurement of peptides and proteins in the deposited marks. To further mimic realistic scenarios, fingermarks were analysed both undeveloped and enhanced by common fingerprint visualisation techniques (white powder and vacuum metal deposition). Based on the chemical profiles produced, a predictive model was then constructed for the purpose of predicting the sex of the donor of unknown fingermarks, such as those that may be discovered at crime scenes.

The technique had a predictive power of up to 86%, demonstrating the potential to differentiate between male and female donors to a degree. There were, however, challenges in this study. Polyethylene glycol (PEG)-based contaminants, routinely used in cosmetics and personal care products, were commonly encountered, interfering with the detection of the actual targets of the analysis. Furthermore, the application of fingermark development techniques also caused interference, with many mass spectra being dominated by the gold nanoparticles used in the vacuum metal deposition method. This suggests the technique may only be truly applicable in the case of undeveloped fingermarks.

Although the technique has a high predictive power, it was not able to determine the sex of the donor in all cases, rendering it unsuitable for conclusively excluding suspects from an investigation based on their sex. However the method could be used to triage fingermarks, allowing investigators to establish which marks are of the greatest importance and which should be prioritised for further study, potentially speeding up forensic investigations.

Heaton & Bury et al. Investigating sex determination through MALDI MS analysis of peptides and proteins in natural fingermarks through comprehensive statistical modelling. 2020, Forensic Chemistry, DOI: 10.1016/j.forc.2020.100271

July 15, 2020 by Locard's Lab

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

If you don’t have a subscription to Forensic Chemistry, see the 50-day free access link or get in touch with the authors.

March 26, 2020 by Locard's Lab

Maggot Analysis with Mass Spectrometry

A new proof-of-concept study by researchers at the University at Albany in New York has developed a mass spectrometry-based technique for the rapid species prediction of blow fly larvae for use in forensic investigations.

Entomological evidence (evidence relating to insects) has proven invaluable to forensic investigations for decades, particularly in the estimation of time since death. Insects which feed on decomposing remains, known as necrophagous insects, will colonise a body in a reasonably predictable pattern, with different insects arriving at different stages throughout the decomposition process. Different species of flies, beetles and mites are commonly encountered. Blow flies in particular will often arrive at the scene within minutes of death to lay eggs on the body. As these eggs hatch, larvae (or maggots) emerge to feed on the decomposing remains. By studying the type and age of insects present at a scene, it may be possible to estimate the time since death, or postmortem interval.

The ability to achieve this hinges on the correct identification of insect species, which is unfortunately not always straightforward. The larvae of different species of blow fly are visually very similar, thus difficult to distinguish by eye. For this reason, maggots are often reared to maturity for species identification, with adult blow flies exhibiting more distinguishing physical differences. Inevitably the rearing of maggots to adulthood is a time-consuming process that requires the expertise of a forensic entomologist.

In recent years, researchers have tried to develop more rapid approaches to insect species identification, particularly using chemical analysis. Researchers at the University at Albany in New York have been applying direct analysis in real time mass spectrometry (DART-MS) to the analysis of insect evidence to provide a rapid species identification tool. In DART-MS, the sample is placed between the DART ion source and the inlet of the mass spectrometer, allowing chemical components in the sample to be ionised and drawn into the MS for direct analysis. DART-MS requires minimal or no sample preparation and results can be obtained almost instantly. Using this technique, Rabi Musah and her team have already demonstrated the ability to determine the species of larvae, pupae and adult flies, highlighting a promising new tool in rapid species identification in forensic entomology.

However, until now this research has focused on the analysis of individual species. In a real-world scenario, maggots present on the body may consist of multiple different species, therefore any techniques developed for rapid species identification of larvae must be able to work with mixed samples. In a recent study, the team have taken the method one step further by examining the potential to identify larvae from mixed species.

Blow flies of various species were collected from Manhattan, New York. Maggots were submerged in 70% ethanol and the solution exposed to the ion source of the DART-MS to produce chemical signatures of both individual species and combinations of species. Mixtures of two, three, four, fix and six different species were analysed. Using the chemical profiles produced, a predictive model was constructed for the subsequent identification of unknown insect samples. Using this model, maggot species could be established with an accuracy of up to 94% and a confidence interval of 80-95%. Individual insect species are readily differentiated, with different species producing distinct chemical profiles. Similarly, mixtures of two different species could also be differentiated. As might be expected, samples containing a higher number of species were more difficult to differentiate.

Although only a proof-of-concept study and further validation is required, the study demonstrates that DART-MS could offer a way of rapidly determining the species of blowfly larvae, thus allowing investigators to establish which insects are present at the scene of a death and work out postmortem interval faster.

Beyramysoltan, S. Ventura, M. I. Rosati, J. Y. Giffen, J. E. Musah, R. A. Identification of the Species Constituents of Maggot Populations Feeding on Decomposing Remains—Facilitation of the Determination of Post Mortem Interval and Time Since Tissue Infestation through Application of Machine Learning and Direct Analysis in Real Time-Mass Spectrometry. Analytical Chem, 2020, In Press.

November 12, 2019 by Locard's Lab

Fingerprint Drug Testing to Detect Drug Use or Contact

The detection and identification of drugs to demonstrate the use of illicit substances has long since been achieved through the collection and analysis of bodily fluids such as urine or blood. However with the inconvenience and invasiveness of collecting bodily fluids from people combined with the risks associated with handling biological fluids, scientists have examined alternative matrices for the detection of drug abuse.

In recent years researchers have demonstrated the possibility of detecting drugs in a less invasive manner, using only a fingerprint. In a recent study published in the Journal of Analytical Toxicology, researchers at the University of Surrey have developed a mass spectrometry-based technique to not only detect illicit drugs in fingerprints, but also differentiate between drug use and drug contact.

Fingerprints were collected from recent drug users undergoing treatment at a drug rehabilitation centre, specifically those who had taken heroin or cocaine in the last 24 hours. Fingerprints were collected both before and after thorough handwashing, with the aim of establishing whether drugs could be detected from both the surface of the hands but also in sweat excreted by the participants. Fingerprint samples were also collected from non-drug users who had simply handled heroin to further establish the detectable differences between those who have used or handled drugs. The fingerprints collected were analysed by liquid chromatography-high resolution mass spectrometry, with a focus on both the drugs and their metabolites (for instance 6-monoacetylmorphine, a compound formed in the body following heroin use).

The experiment successfully detected heroin or its metabolites in every scenario, even if an individual had washed their hands prior to fingerprint collection. However in some instances, the process of hand-washing removed all detectable traces of the drugs, such as in the case of morphine, acetylcodeine and noscapine. Importantly, the technique was able to distinguish between those who had handled illicit drugs and those who had actually taken them, due to the presence of metabolites only formed in the body following drug use. Furthermore, the research demonstrated that it was also possible to detect heroin in the fingerprints of someone who had simply shaken hands with another person who had handled heroin. This highlights an essential factor should such techniques ever become operational in the detection of drug use, stressing the importance of handwashing prior to fingerprint collection to ensure any drugs detected are the result of drug use rather than inadvertent contact with illicit drugs.

The ability to detect drugs in fingerprint could aid legal investigations in a number of ways. Firstly, by demonstrating drug use in known individuals through the analysis of their fingerprints. And secondly, by analysing fingerprints recovered from crime scenes to indicate a person of interest has recently used or handled illicit drugs, potentially guiding police investigations. The full study was published in the Journal of Analytical Toxicology.

Catia Costa, Mahado Ismail, Derek Stevenson, Brian Gibson, Roger Webb, Melanie Bailey, Distinguishing between Contact and Administration of Heroin from a Single Fingerprint using High Resolution Mass Spectrometry, Journal of Analytical Toxicology. https://doi.org/10.1093/jat/bkz088

August 21, 2019 by Locard's Lab

Discovering Donor Characteristics from Bloodstains with Infrared Spectroscopy

From interpreting the incident to pinpointing the perpetrator, the presence of blood at a crime scene can provide clues vital to solving a crime. Since the advent of DNA profiling in the 1980s, police have been able to use DNA to link suspects to crime scenes, making the detection and collection of biological evidence more important than ever before. However successful DNA profiling relies on a positive match with either a DNA profile from a suspect or one stored in a database. With nothing to compare a profile to, the DNA is of limited use and the trail may quickly run cold.

But what if investigators could gain even more information from a bloodstain at a crime scene? What if it were possible to rapidly figure out whether the donor was male or female, or establish their race? And all of this without shipping samples back to the lab.

New research conducted at the University at Albany in New York has demonstrated that it may be possible to establish some individual donor characteristics in a matter of minutes.

Past research has already demonstrated that the biochemical composition of blood differs between males and females and individuals of different races. But the ability to obtain this information on-site at the crime scene in a matter of minutes could change the way body fluids are processed. In a recent study, Prof. Igor Lednev and his team applied a technique known as attenuated total reflection Fourier transform-infrared (ATR FTIR) spectroscopy to blood analysis, with the aim of establishing whether characteristics such as sex and race can be determined from bloodstains.

FTIR is an analytical technique capable of providing information about a material’s chemical information. In brief, the device directs infrared radiation towards the sample. Some of this radiation is absorbed by the material, and some passes through. The sample’s absorbance of this light at different wavelengths is measured and used to determine the material’s chemical information. After analysis a spectrum is produced, which acts as a kind of molecular ‘fingerprint’ of the sample. The different features in the spectrum relate to the different chemical components in the sample.

Infrared spectra were produced by analysing the blood of 30 donors (a mixture of male and females of Caucasian, African American and Hispanic racial origin). From this, researchers could observe any differences occurring between blood from male and females, and blood from members of different races. Using this data, the researchers built a model capable of classifying samples based on their chemical profile. By taking the chemical profile of an unknown bloodstain and comparing it with a model containing bloodstains from numerous different groups, the model can predict the likely classification (i.e. whether the donor was male or female and which racial group they belong to). In this study, it correctly classified bloodstains around 90% of the time.

Using infrared-based techniques has a number of advantages over other methods of analysis. As the technique simply necessitates the direction of light towards the bloodstain, the technique is non-destructive. Inevitably this is perfect for criminal investigations – destroying the evidence is never ideal. IR spectroscopy is also amenable to portability, lending itself well to on-the-go analysis at crime scenes and so potentially saving a lot of time by avoiding sending unnecessary samples back to the lab for analysis.

Although only a pilot study, this research has demonstrated the possibility of establishing donor characteristics through the rapid and non-destructive analysis of bloodstains. The ability to determine features such as sex and race would enable police to significantly narrow down the search for suspects or victims, ultimately preserving valuable time and money. Furthermore, the ability of FTIR to non-destructively analyse evidence on-site renders it an ideal tool for forensic analysis. Inevitably a great deal more research will be necessary, and if the technique ever becomes operational, it would be years before such technology and methods were suitable for deployment to crime scenes and use as evidence in criminal trials.

Mistek et al. Phenotype profiling for forensic purposes: nondestructive potentially on scene attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy of bloodstains. Forensic Chemistry. 2019, In Press.

May 17, 2019 by Locard's Lab

Interview with Lecturer in Forensic Science Dr Kayleigh Sheppard

Dr Kayleigh Sheppard works as a lecturer in forensic science at Liverpool John Moores University.

What is your current job role and what does this entail?

I currently work as a lecturer in Forensic Science at Liverpool John Moores University. My role is divided between lecturing undergraduate and postgraduate students, supervising undergraduate and MSc research projects and conducting research. I teach students across a range of undergraduate courses including BSc Forensic Science, BSc Forensic Anthropology and BSc Policing with Forensics, as well as postgraduate students on the MSc Forensic Bioscience course. Across these courses, I deliver a range of lectures and practical sessions focusing on topics such as Crime Scene Investigation and Forensic Methods with a particular focus on the photography of crime scenes and the evidence contained within them. Photography techniques covered include crime scene photography using natural light and flash, and more advanced photographic methods such as oblique lighting, alternate light source photography and automated 360◦ photography. I introduce the topics and theoretical principles of each topic to the students through lectures and workshops and then give the students hands on experience and the opportunity to develop their practical skills for each of the techniques through practical classes.

The practical classes delivered consist of fingermark enhancement, recovery and comparison, footwear mark recovery, evidence packaging techniques and crime scene documentation and photography. In addition, the students put together everything they have learnt throughout the semester and demonstrate their crime scene investigation techniques using simulated crime scenes that we are able to mock up within our crime scene houses. I supervise a range of student projects at both undergraduate and masters level which investigate advanced photographic methods of crime scenes, using 360-degree photography or mobile technology.

What initially attracted you to your particular field of research?

I have always had an interest and passion for the sciences, particularly biology and chemistry and knew that my future career would be in a scientific field. Whilst at school I was a keen problem solver and enjoyed reading crime and true crime novels. The combination of these traits led me to investigate a potential career in forensic science and so I started my BSc in Forensic Science at Staffordshire University. Throughout the course I was particularly interested in the crime scene aspects and envisaged myself going on to work as a crime scene investigator in the future. Upon completion of my course I had the opportunity to undertake a placement with Staffordshire Police. The placement allowed me to put my knowledge from my degree into practice, alongside crime scene investigators, whilst also providing me with the opportunity to conduct a research project. This project focused on my interest in crime scene investigations whilst incorporating emerging technologies- another interest of mine. The project was entitled “Next generation crime scene recording and forensic data use within criminal investigations”. The project was so well received by the Forensic staff that I wanted to pursue this area further and applied for a PhD investigating the use of 360-degree panoramic photography in a forensic context at Staffordshire University.

Alongside my PhD I was able to teach undergraduate students, introduce them to 360◦ camera technology, and provide them with hands on experience using the technology. The ability to apply my research into the curriculum to enhance the students learning sparked my interest in academia. An academic position provides the best of both worlds, allowing me to pass on my knowledge and experience to the students and teach them about forensic science, whilst also allowing me to continue to pursue my own research avenues. It is very rewarding to teach the students about modern and emerging technologies to assist with criminal investigations and to see their enthusiasm about a topic they may not have been introduced to before. The best part about being a lecturer is having the ability to teach students about topics they are unfamiliar with and pass on that knowledge. The most gratifying part of my job is when a student does not understand a topic or does not enjoy it, but through explanation and discussion using different learning techniques, the students understand the topic and begin to enjoy it.

Can you tell us about the research you’re currently involved in?

Most of the research that I conduct investigates the use of 360◦ panoramic photography for documenting and presenting crime scenes. At first, the research sought to validate the technique, regarding its accuracy for taking measurements at a scene. The research has begun to adapt the technology to answer specific research questions, which may aid crime scene investigators at the crime scene, by adapting the technology to make it do something that it could not do before. For example, the 360◦ camera has been adapted to include alternate light sources for the detection of biological fluids, which are invisible to the naked eye, to simultaneously detect and document them in situ at a crime scene. Further research has also looked into the extent to which modern technologies for documenting crime scenes have been utilised for the presentation of evidence in the courtrooms and the factors that may be affecting the use in courtrooms.

The use of alternate light sources has also branched into other research avenues within the forensic field. Current research being conducted investigates the importance of cleanliness and prevention of cross contamination within Sexual Assault Referral Centres (SARC). The issues with identifying contamination in SARC environments is that in order to ensure cleanliness, the contaminants would ideally be visible. Many biological fluids are invisible to the naked eye and therefore we cannot see them – so how do we know whether they are present on a surface or not? Most biological fluids fluoresce under specific wavelengths of light and enable them to be visualised. Research currently being conducted is seeking to determine the effectiveness of a SARCS-LED light source (CopperTree Forensics Ltd.) for identifying human blood, semen, saliva and vaginal secretions in small volumes (less than 1 μl) on a variety of surfaces typically encountered in SARC facilities. A SARCS-LED enables staff to ‘see’ biological traces, so provides a more targeted forensic clean. This layered approach alongside current ATP testing, and improved cleaning methods, can help to deliver a more thorough service. Using such a light source to identify biological fluids or contamination should enable a more effective cleaning protocol to be employed within SARC facilities, providing a more robust anti-contamination process which is in line with the Forensic Regulator expectations.

Semen and vaginal secretions deposited onto a white vinyl surface. Left – observed under natural light and the biological fluids are not visible to the naked eye. Right – observed under a blue SARCS-LED (445 nm wavelength) and demonstrating biological fluid fluorescence.

What are some of the biggest challenges in your area of research?

Academia can be a challenging place to work and trying to make sure that you maintain the knowledge of the forensic science field whilst it is continually updating can be challenging and often involves lots of reading to stay current, as well as attending training courses and conferences. High profile criminal court cases in forensic science are particularly interesting as they demonstrate to the students the importance and real world impact of their degree and the work they will be conducting in the field, so it is important to stay on top of these as well. At such an early stage in my academic career, being only 26, I felt as if there was a lot of pressure to prove myself worthy. As a result, I take advantage of every opportunity that is presented to me to further my knowledge and experience. It can be challenging to maintain a balance of lecturing, creating engaging and interesting sessions for the students, whilst continuing to conduct research and publish within the field. What keeps me going is my passion and enthusiasm for the subject area and the fact that I can shape the minds of the future.

Finally, do you have any advice for young scientists eager to pursue a career in your field of work?

For any individuals who want to pursue a career as a forensic scientist and get involved with any area of forensic science, make sure that you know what to expect. If you are simply going into this field because of your love for CSI: Crime Scene Investigation on the television that is not enough. The field of forensic science is not always as glamourous as it is often portrayed in the media, and some of the analysis techniques are not always conducted at the drop of a hat. However, saying that, forensic science is such an interesting and exciting field that is constantly evolving – no two days will ever be the same.

If you are interested in pursuing a career in this area you will need to make yourself stand out from the crowd. Over the past few years, this is a field which has become extremely competitive and you need to be able to demonstrate that you are a more suitable candidate than everyone else – what makes you different, what makes you stand out? In order to do this I would highly recommend getting any work experience that you can within the area. Working within criminal investigations can be tricky with active casework, but you do not know unless you ask. Some universities have partnerships with the local police forces so make sure to take advantage of any opportunities they can offer you. If this is not possible, try to get experience in laboratories to demonstrate your ability to follow protocols, work to standard operating procedures and avoid contamination. Alternatively, you could volunteer as a special constable within the police or assist within other police departments. Many of the skills that you obtain from these experiences can be transferred into the forensic field and more importantly demonstrates your commitment to enhancing your knowledge and skill set.

Website: LJMU Kayleigh Sheppard

Twitter: @Kay_Sheppard1

March 22, 2019 by Locard's Lab

Developing Fingerprints on Metals to Aid Knife & Gun Crime Investigations

Fingerprints are something of a staple in forensic science. For over 100 years we have used the unique details of fingerprints to identify victims and suspects, and draw connections between people and objects to place suspects at crime scenes. Fingermarks are encountered on all kinds of surfaces that can have an effect on how easy it is to visualise the mark and for how long the mark persists. As a result, the market is flooded with products for developing fingerprints, from powders to glues to chemical reagents.

Despite the options available, some surfaces, for instance metals, still prove somewhat tricky when it comes to developing prints. This is due to various factors, such as how the chemical results in the fingermark and developing reagents may react with the surface. This is obviously problematic when trying to obtain fingerprints from knives and firearms, a matter of particular importance right now worldwide. For years researchers have been examining methods of improving the detection of fingerprints on metals, including metal vapour deposition and different chemical reagents, but reliable techniques are still few and far between.

Researchers at the University of Nottingham and University of Derby in the UK are using analytical chemistry to solve this problem. Using a technique called Time-of-Flight Secondary Ion Mass Spectrometry, or ToF-SIMS, researchers have developed a way of producing images of fingerprints of various metal surfaces. ToF-SIMS utilises an ion beam which is passed along the surface of the sample, causing ions (charged chemical components) to be emitted from the sample. These are then analysed by mass spectrometry and the results used to produce a kind of map of the surface.

Researchers deposited fingermarks on various types of commonly-encountered metals, such as stainless steel and aluminium, and studied the effects of time on the ability to visualise the prints. Cyanoacrylate (or superglue) fuming, a traditional technique particularly popular when analysing metal surfaces, proved to be unreliable, with the print’s quality degrading rapidly or disappearing completely in just a matter of days. However using this new mass spectrometry-based approach, fingermarks could be visualised in samples up to 26 days old, a vast improvement on traditional methods.

The high-resolution images produced sufficient detail to not only observe ridge detail in the marks, but even the shape and position of individual sweat pores. Furthermore, and perhaps most importantly in a forensic context, the technique is non-destructive. Current methods of visualising fingerprints tend to involve adding a powder or chemical to the print, inevitably altering and potentially contaminating it. But the use of ToF-SIMS ensures the print remains intact, so further development or analysis techniques can be employed if required.

By enabling the visualisation of fingerprints that previous techniques may have failed to reveal, this method has the potential to not only aid investigators as they face the ongoing rise of knife and gun crime, but could also be applied to cold cases. However it is important to note that fingermarks deposited as part of research are not always indicative of real-world samples. In reality the fingerprints we leave behind can vary greatly in the amount of material deposited and the type of material being left behind. Traces of anything handled can be deposited in the fingermark, adding many potential variables to the real-world applicability of this kind of work. Despite this, the study demonstrates a promising new technique for the development of fingermarks on metals, which could have great implications in the investigation of violent gun and knife crimes.

Thandauthapani et al. Exposing latent fingermarks on problematic metal surfaces using time of flight secondary ion mass spectroscopy. Science & Justice. 2018, 58(6).

February 8, 2019 by Locard's Lab

Tracking Movements with Fingernails

When human remains are discovered, investigators will often turn to routine methods such as fingerprinting, DNA profiling and the use of dental records to identify the individual. But in the absence of database records for comparison, such traditional techniques may not prove all that useful, and forensic scientists must look for new ways to identify the unknown.

In recent years the use of stable isotope analysis has aided forensic investigations, particularly in establishing the geographic origin of unidentified human remains. Isotopes are different forms of an element. For example, oxygen has three naturally occurring stable isotopes: O¹⁶, O¹⁷ and O¹⁸. These isotopes are incorporated into substances in the environment (such as water) in varying ratios. The relative abundance of isotopes can be influenced by various factors in a process known as isotopic fractionation. It has been found that isotopic ratios can be related to different regions of the world. For example, the tap water in one country may have a completely different isotopic signature in comparison to water in another country. How does this relate to the isotopes found in our bodies? Well, you are what you eat. As you consume food and water from a particular area, the atoms in our bodies express abundances similar to the food and water consumed.

This provides the basis for using isotope analysis to trace materials back to a certain geographic region. It has already been demonstrated that the isotopic analysis of bones, teeth and other bodily tissues can allow for individuals to be traced to particular locations, typically through the analysis of oxygen, hydrogen and sulphur isotopes. However last year, researchers at the University of Utah took a different approach, this time focusing on fingernails.

As with bones and teeth, the isotopic content of our fingernails will be affected by factors such as the food and water we consume. As fingernails are estimated to grow at a rate of 3-4mm per month, they are a prime target for studying isotopic patterns in an individual over a shorter timespan (less than six months as oppose to years). This is by no means the first study of isotope abundances in fingernails, but previous research has typically focussed on single timepoints rather than tracking the same individuals over time. As global travel becomes more commonplace, it is increasingly likely that human remains could have originated from any part of the world. Therefore, we need to understand how travel can cause changes in isotope abundances within the body.

This study aimed to establish whether fingernail isotope ratios were different in a group of local people in comparison to non-locals who had recently moved to the area (in this case Salt Lake City in the United States). Over a period of a year, fingernail clippings were collected at multiple timepoints from a group of volunteers, about half of which were local residents and the rest individuals who had recently arrived from various locations across the US and the world. The fingernail clippings were cleaned (to remove surface components and contaminants that could interfere with the analysis) and subjected to analysis by isotope ratio mass spectrometry (IRMS). IRMS is a particular type of mass spectrometry that allows us to measure the isotopic abundance of certain elements typically hydrogen, carbon, nitrogen, and oxygen. You can read more about IRMS here.

The isotope values of samples from residents were used to construct a baseline of expected values for the area, with isotope values from non-residents’ samples being compared with these. Initially, samples from non-residents showed a wide range of isotopic values, which is to be expected given they had only recently moved to the area. Some residents did fall within the expected range of locals, but these participants had moved from relatively nearby locations, which could explain the similar relative isotopic abundances. However after about 3 months, the fingernail isotopic patterns shifted until the non-residents could no longer be distinguished from the residents. This indicates that although the relative abundance of isotopes in our fingernails can shed some light on geographical movement, it can only provide information relating to the past few months. Inevitably there will always be a certain amount of error associated with such analyses, with variation from the likes of short-term travel and random dietary changes being impossible to account for.

Mancuso, C. J, Ehleringer, J. R. Resident and Nonresident Fingernail Isotopes Reveal Diet and Travel Patterns. Journal of Forensic Sciences. 2019, 64(1).

December 3, 2018 by Locard's Lab

Interview with Forensic Taphonomist Professor Shari Forbes

What is your current job role and what does this entail?

Forensic taphonomist Professor Shari Forbes.

I am a Canada 150 Research Chair in Forensic Thanatology and the Director of the Secure Site for Research in Thanatology (SSRT). The SSRT represents the first human taphonomy facility in Canada and is the only place in this distinct climate where we can study the process of human decomposition through body donation. My role is to lead and conduct research at this facility, specifically in the field of forensic thanatology and decomposition chemistry. This role also involves engaging collaboratively with our external partners who can benefit from the research and training we conduct at the facility, notably police, forensic services, search and rescue teams, military, human rights organisations, and anyone involved in death investigations.

What initially attracted you to your particular field of research?

I have always had a passion for science and knew that I wanted to pursue a career in a scientific field where I could clearly see the impact of my work. When I was in high school, I enjoyed reading crime novels and probably understood what forensic science entailed better than most people (this was before the advent of CSI, Bones, NCIS, etc.!). My love of science combined with my interest in criminal investigations naturally led to pursuing a career in this field. At the time, there was only one university in Australia that offered a forensic science degree so the decision of where and what to study was relatively easy. Although chemistry wasn’t my strongest subject at school, I enjoyed the degree because it applied chemistry to forensic science and in this way, I could understand how my skills would help police investigations.

Can you tell us about the research you’re currently involved in?

My research focuses on the chemical processes of soft tissue decomposition and the by-products released into the environment. This can include compounds released into air, water, soil, textiles, or anything surrounding the body. The majority of my research at the moment focuses on the release of volatile organic compounds (VOCs) into the air to better understand the composition of decomposition odour. Although this is not pleasant work, it is very important to understand the key compounds used by cadaver-detection dogs for locating human remains. If we can identify the key VOCs and determine when they are present, we can enhance the training and success of cadaver-detection dogs in complex environments such as mass disasters.

You were heavily involved in the establishment of the Australian Facility for Taphonomic Experimental Research. What were some of the greatest challenges in this and how has the facility since developed?

It took approximately 3.5 years to establish AFTER from the day we started planning it to the day it opened in January 2016. I have since realised this is not that long compared to some of the other facilities that are currently operating but there were challenges and hurdles that we faced along the way. In Australia, establishing a human taphonomy facility essentially requires three things: 1) an organisation willing to lead and support it; 2) a body donation program; and 3) accessible land that can be used for taphonomic research. We were fortunate that the University of Technology Sydney (UTS) had these three things and we also had the financial and in-kind support of all of our partners including academic institutions, police services and forensic laboratories. Once we had this support and made the decision to proceed, we still needed to seek approval from our local council to use the land for this purpose; apply for funding to build the facility; and apply to have the facility licenced to hold human remains for the purposes of taphonomic research and training. Thankfully, everyone we engaged with was highly supportive of the facility and willing to work with us to ensure we followed all legislation and regulations. We also ensured we had a strong communication plan to raise awareness with the general public about the benefits of these facilities and how important the research is to assist in the resolution of death investigations.

The Australian Facility for Taphonomic Experimental Research

Since opening, we have been amazed by the general interest in AFTER and the number of people wanting to donate their body. We have also increased our partnerships to benefit more police and forensic services as well as others services such as the cemetery industry. We are currently planning to provide more training opportunities, particularly relating to disaster victim recovery and identification, and to establish more AFTER facilities across Australia to better represent the diverse climates experienced across the country.

You recently left the University of Technology Sydney to relocate to Canada. How will your role and research be changing as you make this move?

I was honored to be the Director of AFTER and it was a difficult decision to leave Australia. However, I recognise the importance of these facilities and the need to establish them in other countries so when I was asked to open Canada’s first human taphonomy facility, it was an opportunity I could not turn down. My experience in Australia has already assisted greatly in establishing the facility in Quebec and we will certainly be able to open the facility much more rapidly as a result. Like in Australia, we hope it acts as a template for future facilities across Canada since this country also has very diverse climates. In reality, neither my role nor my research will change significantly. The greatest change will be the climate and its impact on the process of decomposition!

Finally, do you have any advice for young scientists eager to pursue a career in your field of work?

It sounds like a cliché, but I always encourage students to pursue a career in a field they are passionate about. If you had told me 20 years ago that I would being leading not one, but two ‘body farms’ I would never have believed it (especially after just reading Patricia Cornwell’s novel that gave these facilities that name!). But I knew I was passionate about studying a science that was deeply applied and had a clear impact on society. I had no idea where it would lead me or even if I would get a job in the field, but without that passion, I would not have been motivated to do any of the things I have done; namely: complete my degree, continue on with a PhD, do research in decomposition chemistry, and ultimately become an academic so that I could continue my passion of conducting forensic taphonomy research. So if you are going to do something for the next fifty years, make sure it is something you love doing!

Find out more on the Secure Site for Research in Thanatology website.

This is Part 17 of our series of interviews with forensic professionals. If you’re a forensic scientist (academic or industry) or a crime scene investigator and would like to be part of this series of interviews, get in touch by emailing locardslabblog[at]gmail.com.

October 22, 2018 by Locard's Lab

Drug Detection at Your Fingertips: Illicit Drugs in Fingerprint Sweat

Researchers have developed a new tool for the rapid detection of a number of illicit drugs using only the sweat of an individual’s fingerprint.

Typically, the procedure to test for drugs in human beings necessitates the collection of blood or urine and laboratory-based analysis by gas or liquid chromatography with mass spectrometry. Unfortunately these standard methods are somewhat invasive, require potentially time-consuming laboratory-based analysis, and use complex pieces of analytical instrumentation requiring a trained operator to use. They are inevitably unsuitable for rapid, in-situ screening of potential drug users.

Researchers at the University of East Anglia and Intelligent Fingerprinting Ltd (a spin-out company from the university) have been working on a method of conducting simple, rapid drug analysis using sweat from a person’s finger. The technique has been developed to detect four classes of drugs – cannabis, cocaine, amphetamines and opiates, with cannabis being detected based on the presence of Δ⁹-tetrahydrocannabinol (THC), cocaine on the presence of benzoylecgonine, and opiates via the detection of morphine.

The finger of an individual is firmly pressed onto the Drug Screening Cartridge. This is then filled with a buffer solution before insertion into the reader for analysis. Capable of detecting drugs down to the picogram level, the system is a fluorescence-based lateral flow competition assay containing four drug-bovine serum albumin conjugate lines on a nitrocellulose test strip. In short, when a sample is introduced to the test strip, fluorescently-tagged antibodies pass over the conjugate lines. As these antibodies are specific to each drug class of interest, if that drug is present they will bind to the drug. At the end of the test, a fluorescence signal is measured. If none of the four drug classes were present, a maximum fluorescence signal will be obtained. However if any drugs were present to bind with the antibodies, there will be a decrease in the fluorescence signal proportional to the drug concentration. Within about 10 minutes, the device then gives a simple pass/fail response, requiring no specialist knowledge or excessive training to operate and interpret the results.

Furthermore, the technique has also been demonstrated to be effective when applied to the deceased. Researchers worked with a number of UK-based coroners to obtain fingerprint sweat samples from 75 deceased individuals. The most common drug detected was opiates, which is a logical finding considering the number of terminally ill patients who are prescribed morphine during palliative care.

In order to compare the new technique with those typically employed in the detection of drugs in human beings, analysis of blood samples was conducted by LC-MS-MS. The results between the two methods correlated well, with the accuracy between DSC of fingerprints and LC-MS-MS of blood being 88-97%, depending on the drug. This demonstrates the effectiveness of the method and its ability to stand up to existing techniques, though there are inevitably some shortcomings. Authors of the study have stated that there are known accuracy issues with lateral flow measurement devices, thus this new technology should be used as a presumptive screening method prior to confirmation by mass spectrometry. Furthermore, the range of target drugs is clearly currently limited, though future development could no doubt enable other classes of drug to be included.

Full details of the findings can be found in the Journal of Analytical Toxicology.

References

Hudson, T. Stuchinskaya, S. Ramma, J. Patel, C. Sievers, S. Goetz, S. Hines, E. Menzies and D. A. Russell, J. Anal. Toxicol., 2018, 6–10.

Forensic Magazine. Fingerprint Drug Screen Test Works on the Living and Deceased. [Available online] https://www.forensicmag.com/news/2018/10/fingerprint-drug-screen-test-works-living-and-deceased