The Smell of Death: Confirming Decomposition using Volatiles in the Air

Odour mortis, or the ‘smell of death’, refers to the chemicals released from the body during decomposition. Renowned forensic anthropologist Arpad Vass, who has studied the chemical changes occurring in the body after death for many years, recently shared the details of a particularly interesting scenario. The article, published in the May 2019 issue of Forensic Science International, details a fascinating case in which the occurrence of human decomposition was demonstrated based solely on chemical compounds in the air for the first time, without any human remains actually being found at the scene. The article doesn’t specify suspect or victim details, but anyone familiar with the case will recognise it instantly.

First, a brief introduction. In 2008, a woman was charged with the murder of her daughter, allegedly storing the victim’s body in the boot of her car for several days before disposing of the remains and dumping the car. Police had initially been alerted to the incident by the suspect’s parents, who had picked up their daughter’s abandoned car and noticed a foul decomposition-like odour coming from the vehicle. Coupled with the fact they had not seen their granddaughter in several weeks, the suspect’s mother promptly called 911.

The police soon took possession of the car and agreed that the scent of decomposition was emanating from the vehicle. Numerous cadaver dogs, specifically trained to detect odours from decaying bodies, alerted to the back of the car, further suggesting some kind of decomposing remains had been stored in the boot of the car. Fly pupae were also discovered. Entomological evidence is frequently associated with decomposing human remains, with flies and various other insects known to visit corpses to feed or lay eggs. Although no human remains were found in the car, several weeks later the body of the missing girl was found in a wooded area near the suspect’s home, and the case promptly turned into a murder investigation, with the victim’s mother as the prime suspect. However with minimal physical evidence linking the body to the suspect’s car, law enforcement turned to a somewhat unconventional tool to aid their investigation.

Various pieces of evidence were recovered from the vehicle, including segments of carpet, scrapings from the tyre wells, and various pieces of rubbish found in the car. Interestingly, investigators also collected some air samples from the boot of the car. Air can be sampled from remote locations using a technique that utilises air pumps to draw in gaseous analytes from the environment and capture them in a sorbent trap. This collection of trapped compounds can then be transported to a laboratory for analysis. In this case, about 35L of air was collected from the vehicle into a type of sorbent tube, then analysed using gas chromatography/mass spectrometry (GC/MS). GC/MS is a well-established analytical technique, allowing scientists to separate the individual chemicals in a mixture and identify those components. You can read more about how mass spectrometry works here.

This process allowed researchers to figure out exactly which volatile chemicals were present in the suspect’s vehicle and establish whether these are everyday compounds likely to be found in a car, or if they had some other source.

In the years leading up to this case a great deal of research had been conducted at the University of Tennessee’s Anthropological Research Facility. At this facility researchers were investigating, among other things, the odours produced during the decomposition of a human body. The odours created during this process are the result of volatile compounds produced as the body decomposes, and research has demonstrated that hundreds of individual chemical components are formed during this complex process. As part of research at the university, researchers had constructed a vast database of hundreds of chemicals detected during the process of human decomposition, including the different decomposition stages at which those chemicals appear. By comparing the chemicals detected in the vehicle with those stored in the database, it was possible to identify compounds known to be produced during the decomposition process. There was an 80% match between the compounds detected in the boot of the car and those chemicals considered to be relevant to human decomposition. Furthermore, unusually high levels of chloroform were also detected in the boot of the car.

The results from the air samples collected and chemical extracts from various other artefacts in the car led the researcher to conclude that there was a very high likelihood of a decomposition event occurring in the boot of the car. Many of the compounds detected in the vehicle could only be logically explained by the presence of decomposing remains.

Despite these findings (and various other pieces of evidence presented in court), the jury reached a verdict of not guilty for the charge of murder. Not too surprising an outcome, considering the use of air analysis to detect decomposition had not previously been used in a legal investigation. However in closing arguments, the defence stated that the victim had in fact been placed in the vehicle for transport (claiming the victim’s death had been accidental), ultimately confirming the results of the analysis.

 

Vass, A. A. Death is in the air: confirmation of decomposition without a corpse. Forensic Sci. Int. (2019). doi:10.1016/j.forsciint.2019.05.005

Vass, A. A. Odor mortis. Forensic Sci. Int. 222, 234–241 (2012).

 

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Detecting Homemade Bombs & Explosives in Sweat

Detecting Homemade Bombs & Explosives in Sweat

Improvised explosive devices (IEDs) are often used in the implementation of terrorist attacks, for instance the 2005 London underground bombings, the suicide bomb attack during a concert in Manchester, and the 2015 Paris attacks. Unfortunately the components required for building these devices are commercially available and the bombs relatively easy to construct.

Many explosives leave a characteristic trace after being handled or detonated, and it is essential that investigators can rapidly identify the components used in homemade explosives. Furthermore, the ability to trace the explosives back to particular individuals and terrorist cells is essential in preventing future attacks. Unfortunately effectively detecting and tracing explosives and explosive precursors can prove difficult. On top of this, after the production and implementation of IEDs, it can be difficult to prove a suspects’ involvement in bomb construction.

Researchers at King’s College London and Northumbria University have been working on developing new ways to detect homemade explosives.

The newly developed approach, recently published in the journal Analytica Chimica Acta, uses a technique known as ion chromatography high resolution mass spectrometry (IC-HRMS) to separate and detect chemical components. By applying the technique to compounds commonly encountered in the analysis of explosive residues, the method was shown to be effective in detecting a large number of components used to make bombs, capable of detecting just trace amounts of the chemicals faster than previous techniques.

Upon developing this method, the team of researchers then demonstrated that the approach could be applied to the analysis of human sweat, with the aim of indicating an individual has recently handled explosives. Participants were made to handle Pyrodex powder, a black powder propellant used in firearm cartridges. After handling the powder for a few minutes, palm sweat and fingermark samples were then collected at numerous timepoints over several hours. Analytes related to the explosive material were readily detected using the method. The real-world implementation of this technique could help prove contact between a suspect and explosive material or explosive precursors.

 

Gallidabino et al. Targeted and non-targeted forensic profiling of black powder substitutes and gunshot residue using gradient ion chromatography – high resolution mass spectrometry (IC-HRMS). Analytica chimica acta. 2019, In Press.

Developing Fingerprints on Metals to Aid Knife & Gun Crime Investigations

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).

Tracking Movements with Fingernails

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).

 

Tracking Illicit Drugs with Strontium Isotope Analysis

Tracking Illicit Drugs with Strontium Isotope Analysis

The manufacture and distribution of illicit drugs such as heroin is a primary focus of many major law enforcement organisations worldwide, including the Drug Enforcement Agency (DEA) in the United States and the National Crime Agency (NCA) in the United Kingdom. Unfortunately, as drug shipments pass hands between dealers and cross borders so rapidly, it can be difficult if not impossible to trace a batch of drugs back to an initial manufacturer. As a result of this, the chances of locating and arresting the manufacturers of illicit drugs can be slim.

To a forensic drugs analyst, a whole range of characteristics can be examined and used to classify and compare different batches of the same drug, including physical appearance, packaging, and chemical composition. To an extent, heroin chemical signatures are already beneficial in comparing different batches of the drug in attempts to establish links and possible sources of the narcotics. This may be based on agents or adulterants a product has been cut with, and the relative concentrations of those substances. The manufacturing process itself can vary in terms of chemicals and apparatus used and the skills of the manufacturer, resulting in further characteristic differences in the chemical profile. However these differences may not be distinct enough to be valuable and are certainly not able to pinpoint the country from which a batch originated. Though there is still no reliable method of tracing an illicit drug back to a particular location, ongoing research is aiming to change this.

One method of studying the history and even origin of a sample is to use isotopic composition. Isotopes are different forms of elements that are incorporated into substances in the environment in varying ratios and abundances, influenced by a number of factors that can alter these ratios. These processes can be described as isotopic fractionation. Interestingly, isotopic ratios can be characteristic to different regions of the world, enabling certain materials to be traced back to the geographic region based on the ratios of particular isotopes contained within that material. With this in mind, they have often been used to trace unidentified human remains to a particular location or study the origin of food products. Focusing on isotopes allows for heroin samples to be studied and compared based on regional characteristics as oppose to the variation caused by the production process.

For the first time, researchers at Florida International University have utilised strontium isotope ratio analysis to determine the provenance of illicit heroin samples. 186 unadulterated, undiluted heroin samples of known origin were obtained from a number of geographic regions including Southeast Asia, Southwest Asia, South America, and Mexico. Of a particularly challenging nature is South American heroin and SA-like Mexican heroin, which can be extremely difficult to differentiate based on their chemical compositions alone. Heroin samples were dissolved via a microwave-assisted acid digestion method before being subjected to a technique known as a multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS). This instrument utilises an inductively coupled plasma ion source to ionise target analytes, which are then separated and analysed by the mass spectrometer. The use of MC-ICP-MS allows for the strontium concentration of particular samples to be determined. The strontium isotope ratio (87Sr/86Sr) value of each individual sample was then compared with the overall mean values of ratios from different regions in order to establish the likely origin of that particular heroin sample. Samples from the same geographic region would be expected to exhibit a similar isotope ratio.

icpms

Multi-collector inductively-coupled plasma mass spectrometer (MC-ICP-MS) Source: www.thermofisher.com

The results demonstrated the possibility of differentiating between heroin of different geographic origin. South American and Mexican heroin samples were correctly classified 82% and 77% of the time respectively. South East and South West Asian heroin samples were somewhat more difficult to differentiate due to more of an overlap between strontium isotope ratio values. SE Asian samples were correctly classified 63% of the time and SW Asian samples only 56% of the time. It is not clear whether this elemental strontium is endogenous or the result of external contamination, but either way it is sufficiently characteristic to be associated with a particular geographic location.

The strontium isotope composition of heroin can be affected by a number of factors, including the soil in which components are grown and groundwater in the area, which can result in region-specific isotope compositions. The use of strontium isotope ratio analysis has presented promising results in the origin determination of illicit heroin. Although a larger scale study incorporating samples of a more worldwide origin would be ideal, initial results suggest that this technique could allow for an unknown illicit drug sample to be traced back to a country of origin, aiding criminal intelligence agencies in the war against drugs.

 

Debord, J., Pourmand, A., Jantzi, S., Panicker, S. & Almirall, J. Profiling of Heroin and Assignment of Provenance by 87Sr/86Sr Isotope Ratio Analysis. Inorg Chim Acta. In press (2017).

Instant Insect Identification to Aid Forensic Entomology Investigations

Instant Insect Identification to Aid Forensic Entomology Investigations

During the investigation of a suspicious death, entomological (that is, insect-related) evidence may be able to provide vital clues as to when the victim died. Determining time since death, or post-mortem interval, can be one of the most important aspects of such an investigation, so it comes as no surprise that a great deal of research has been directed towards improving these estimations.

Insects can play a huge role in estimating time since death. Various types of species of insect will often visit the scene of a death in a relatively predictive manner, either to feed on the decomposing remains (known as necrophagous insects), to prey on other insects present, or to find a suitable place to lay their eggs. Blow flies, a group which includes common flies such as the bluebottle and the greenbottle, are often of particular interest. Forensic entomologists will typically study the insects, eggs and larvae present at a death scene, utilising the type of bugs found and their stage of development to track back to the likely time at which they arrived, thus when the victim may have died. However in order to accurately do this, entomologists must often collect insect specimens for closer inspection and even to rear to adulthood in order to determine the exact species, which is evidently a time-consuming process requiring a high level of expert knowledge.

For the first time, researchers at the University of Albany have applied a technique called direct analysis in real time with high resolution mass spectrometry, or DART-HRMS for short, to the analysis of blow fly eggs. Published in the latest issue of the journal Analytical Chemistry, the technique has demonstrated the possibility of almost instantly differentiating between different fly species based on the amino acid profiles of the eggs.

DART-MS, developed in 2005 by Dr Chip Cody of JEOL, is an ambient ionisation mass spectrometry technique that allows for samples to be directly analysed without any time-consuming sample preparation steps, and perhaps most importantly without destroying the sample. The sample is simply presented in its native state between the ion source and the inlet of the mass spectrometer, enabling compounds present in the sample to be ionised and drawn into the instrument for analysis and identification.

dartms

Sampling interface of DART-MS. Source: Wikimedia Commons

During this investigation, researchers used pieces of pork liver to attract a number of different blow fly species before transporting them to the laboratory. The flies were reared until they lay new eggs, which would be the focus of the analysis. The study utilised specimens of a number of species, including Calliphora vicinia, Lucilia coeruleiviridis, Lucilia sericata, Phormia regina, along with specimens from the Phoridae and Sarcophagidae families. Even to the eye of an expert, the eggs of these specimens are often indistinguishable. The eggs were simply placed in an ethanol solution and the mixtures directly subjected to DART-HRMS analysis.

The technique focused on the analysis and identification of amino acids in the eggs, essentially enabling researchers to produce a chemical fingerprint unique to eggs of a particular species. Examination of the mass spectra showed that the different species exhibited a unique chemical fingerprint, and by using multivariate analysis it was possible to better visualise the similarities and differences between amino acids detected in the eggs of different species.

Unsurprisingly, many amino acids were common to multiple species. For instance, alanine, isoleucine and proline were detected in four of the species, whereas valine was detected in all but one of the egg samples. However some compounds were unique to particular species, and it is these unique amino acids that will prove to be most beneficial in differentiating between the eggs of different species. For instance, glutamine and tryptophan were only present in the eggs belonging to P. regina. Interestingly, the research also demonstrated the ability to distinguish between families as well as species, with some compounds only detected in the eggs of specific families.

By using this particular technique, almost instantaneous identification could be achieved. Of course this research has included only a very limited number of species, thus a much bigger investigation would be necessary before the technique would really be beneficial to a legal investigation. Not only would further species need to be included, but another potential development would be the production of a chemical profile database against which unknown insect samples could be compared. Developed further, the use of DART-MS could save investigators a lot of time in the identification of insects of forensic interest.

 

References

Cody, R. B., Laramée, J. A. & Durst, H. D. Versatile New Ion Source for the Analysis of Materials in Open Air under Ambient Conditions. Anal. Chem. 77, 2297–2302 (2005).

Giffen, J. E., Rosati, J. Y., Longo, C. M. & Musah, R. A. Species Identification of Necrophagous Insect Eggs Based on Amino Acid Profile Differences Revealed by Direct Analysis in Real Time-High Resolution Mass Spectrometry. Anal. Chem. (2017) In Press

 

Interview with President of IsoForensics Inc., Lesley Chesson

southern-utahDifferent forms of elements–called isotopes–are found everywhere in the environment. These isotopes are incorporated into materials in varying ratios and the abundances of different isotopes thus serve as a record of the material’s formation. Analysis of a material for its distinct isotope signature can subsequently be used to reveal its history. Investigators have applied stable isotope analysis to a variety of materials of forensic interest including drugs, explosives, money, food, ivory, and human remains. For example, the isotopes in human hair protein can reveal the age of an individual, what s/he ate, and even how often (and where) s/he travelled.

What is your professional background and how did you come to be involved in IsoForensics?

I have a master’s degree in biology, with a lot of microbiology and chemistry experience. I entered the world of isotope forensics when I was hired to raise Bacillus subtilis (a cousin of the anthrax bacterium) under a variety of conditions – in liquid media, on agar plates, with different nutrients, etc. Because organisms record information about the environment in the isotopes of their tissues, the goal of this project was to develop models that allowed investigators to predict the growth conditions of a dangerous bacterium–such as anthrax–from its isotopic characteristics.

From its start in academia, IsoForensics developed into a private analytical services and research firm that explored novel forensic applications of isotope analysis. I enjoyed the challenges offered by that exploration. Since my first work on the B. subtilis project, I’ve been involved in other projects on human remains, foods and beverages, illicit drugs, and explosives.

Tell us about the work IsoForensics is involved in and what kind of clients do you typically work with?

Currently, IsoForensics provides a lot of human remains testing in unidentified decedent cases. The goal is to use the isotope records contained in hair, nails, bone, and teeth to reconstruct the travel history of individuals and provide new evidence on their origins: Were they local to the area of discovery? Had they traveled prior to death? Where might they have traveled? We work with a variety of law enforcement groups in this casework.

In addition to service work, we conduct basic and applied research through funded grants and contracts. One recent project has started to investigate the origins and ages of seized elephant ivory to understand the structure of illegal trade networks in Africa and Asia.

What are some of the most common sample types you are asked to analyse, and does anything pose a particular challenge?

In any given month, we can analyze a variety of materials – human and wildlife remains, illicit drugs, explosives, etc. One of the most challenging measurements we make is for strontium isotope ratios. There is so little strontium contained in organic materials that prep work takes place in clean lab settings. The preparation of materials for radiocarbon dating is also challenging since we must be extremely careful about contamination of “old” materials with “modern” carbon. However, these challenges are worthwhile since strontium isotopes can provide potentially useful geolocation data about materials while radiocarbon dating provides quantitative information on the “age” of materials.

Are there any areas of isotopic analysis that could benefit from further research and development?

Yes. Isotope forensics benefits from better and better models/methods for interpreting data. It’s one thing to compare isotope measurement results from sample to sample or from sample to a reference databank, but it’s another thing altogether to understand the process(es) driving isotopic variation in materials. For example, are the results we observe due to differences in TNT manufacturing process? Or coca plant physiology? Or elephant diet?

Isotope analytical techniques also change over time as better instrumentation is developed. Understanding the impact of different analysis techniques on measured isotope ratios is extremely important when comparisons are made – especially in legal settings. A major focus of the field is the standardization of practices and protocols, to generate comparable results over time and space (e.g., from lab to lab).

How has the need for isotope analysis in forensic investigations changed over the years, if at all?

The forensic application of isotope analysis has been increasing the past 10-20 years. This is partly due to changes in analytical techniques, which have made isotope ratio measurements faster and cheaper. In addition, those who could benefit most from forensic isotope data–law enforcement, regulators, etc.–have become more aware of the technique and it potential usefulness in various types of investigations. We as forensic scientists and isotope analysts can do even more to spread awareness about the technique and its many applications.

Finally, do you have any advice for students hoping to pursue a career in this field of work?

Isotope analysis is one (extremely useful!) tool in a forensic scientist’s toolbox. Having a background and training in other areas–such as anthropology, analytical chemistry, biology, biochemistry, geology, law, or statistics–can be very important when applying isotope analysis techniques and interpreting the resultant data. The field of isotope forensics is relatively small compared to some other forensic disciplines, so be sure to read papers, attend meetings, and network with scientists working in the field.

Visit the Isoforensics Inc. website for more information.