The essence to solving crimes is evidence. I don't believe in the perfect murder. You always take something with you, or you leave something behind. New forensic methods are making the invisible visible. Most trace evidence comes from nature. This amount of soil in the palm of my hand contains more individual organisms than there are the number of people that live on this whole planet.
But there remains much to discover open questions to answer, technologies to develop. The question is how long has this trace been here? Only when I know that can I link it to the facts. Time is also relevant in other investigations: I’m hoping that we can say, for instance, this puparium is 2 to 2 ½ years old or this puparium is 8 weeks old. Will the perfect crime soon be a thing of the past? Every flowering plant produces it. It wafts through the air, often invisibly, attaching itself to everything that moves: Pollen leaves its mark everywhere and can even help solve crimes: The cell wall surrounding each individual grain is so stable that pollen can survive millions of years.
Vienna. The Austrian capital is home to THE expert in the field of forensic pollen analysis. Martina Weber heads the Department of Structural and Functional Botany at the University of Vienna. She is one of a few scientists worldwide working in the field of forensic pollen analysis. On a sunny day in May, in Lower Austria, road workers working in the Höllental, a popular tourist destination near Vienna, made a discovery that starkly contrasted with their idyllic surroundings: they found a corpse lying in a roadside ditch.
The Criminal Investigation Department of the State of Lower Austria launched immediate investigations. The body was wrapped in a blanket and it was immediately clear that there had been a violent crime. So we took up the investigation.
The crime-scene and homicide teams from the state’s criminal investigation department drove out to Höllental. We were quite certain that the location where the body was found was not where the crime had been committed. The investigators soon turned to Martina Weber.
The dead man was wrapped in a blanket. It most likely came from the primary crime scene or at least from the perpetrators. And that's why we examined this blanket thoroughly. Of course, you can't wash the whole thing, but you cut small pieces out of it where there is notable clumping, or where you suspect there might be something interesting underneath. After washing the sample, it is centrifuged to separate it into its component parts.
Palynology is the scientific term for pollen analysis the "study of scattered dust". The first person worldwide to solve a murder case with the help of forensic palynology was Wilhelm Klaus, Martina Weber’s mentor, here at the University of Vienna. At the time the suspect had the whole of Vienna on tenterhooks, because the murder victim could not be found. Over the course of a year, he had named a wide variety of places in the Vienna region.
But nothing was discovered until professor Wilhelm Klaus showed up. He was a palaeobotanist here at the University of Vienna, and a biologist by training. He had the brilliant idea of testing the suspect's shoes and clothing for pollen.
Among the thousands of pollen samples Prof. Klaus found was fossilized Hickory pollen from a long extinct species that once grew near what is now the village of Spillern in Lower Austria. Confronted with this finding, the suspect confessed and revealed the body's exact location.
Today, many know about DNA traces and how to avoid leaving them. The criminals too. But pollen traces are everywhere and are extremely persistent. Martina Weber is working on a case that dates back almost 2000 years.
It is not a crime case, but rather the scene of a natural disaster. She is attempting to correct a possible historical error. When the volcano Vesuvius erupted, it completely buried the ancient city of Pompeii. The ash preserved the city and many of its inhabitants in the last seconds of their lives. The eruption date of August 24, 79 CE derives from the letters of Pliny.
But other writings and findings suggest that the eruption did not occur until October. To investigate this discrepancy, samples were taken from the nostrils of some of the victims. Martina Weber is now examining them to determine from the inhaled pollen what season the samples are from. Free flying pollen gets caught in the ethmoid bone, the bone at the end of the nasal cavity. It usually stays there for about forty minutes before it is exhaled back out through the nose. By examining residual pollen on a corpse's ethmoid bone, conclusions can be drawn about the last forty minutes of that person's life.
There are four samples to examine. The pollen from the nostrils is centrifuged and then boiled in a mixture of acetic acid, anhydrite, and sulphuric acid. This process removes everything but the pollen wall. Martina Weber then begins the counting process under the light microscope. Gradually she determines which pollen grains are represented in the sample, and in what frequency they occur. Based on the microscope-count, a so-called pollen diagram is created.
What we have here is a sample from a child's skull, specifically from the nasal base. We examined the material and discovered a diverse array of plants, plants which indeed grew in Pompeii, like pine or oak, olive trees, then Artemisia, and there was also a Hedera helix pollen grain or rather lots of them. That’s ivy, ivy pollen; ivy tends to flower later in the year. And that of course was relevant to our research question of whether we can ascertain if the volcano really erupted on August 24th or much later in the year; there are big debates on the matter. Should the eruption date of mount Vesuvius on 24th of August, 79 CE be moved to the flowering period of ivy in the autumn? It would be a sensation if the date of this world-historical event were to be changed on the basis of a pollen examination! The Höllental case has not yet been solved either.
The tests for pollen on the woollen blanket are still in progress. Barely visible to the naked eye and yet so rich in information... The pollen grains swirling from flower to flower have breezed into the ranks of forensic methods. But they are not alone.
With its unique profile, the soil in which the plants grow is also valued in investigations. Lorna Dawson is one of the world's leading experts in the field of soil forensics. She is consulted by police departments from all over the world.
This amount of soil in the palm of my hand contains more individual organisms, living together than there are the number of people that live on this whole planet. So just imagine how many that really is. This is teeming with life.
And that information can tell us so much about the soil that is the home for these multiple organisms. The microorganisms in the soil are responsible for its structure and fertility. They break down toxins, help plants absorb nutrients and contribute to their resilience. But can soil also bear witness to a crime? Galloway Forest Park in Southwest Scotland is the largest contiguous forest in the United Kingdom.
Tourists and hikers are attracted by the unspoiled natural environment with its diverse animal and plant populations. But on June 12, 2019, walkers encountered more than pristine nature. Hidden beneath some branches in a hollow in the earth, they discovered a corpse. Investigators quickly established that it was a woman who had been missing for weeks and that the cause of death was unnatural. They soon had a suspect.
Police sent several soil samples to Lorna Dawson for analysis. The scientist compared the soil samples from where the body was found with samples collected from the suspect's surroundings. There's a whole range of different methods that can be used to characterise the soil biology. And there's still a lot of research to be done to make sure that when you're comparing an unknown sample with a known sample that the same procedure is carried out because that's absolutely vitally important for any analysis that is carried out on the unknown a question sample.
You have to use the same procedure for any reference sample that's going to be compared with it. What about the soil samples in the current murder investigation? Could Lorna Dawson help to solve the case? In the investigation, the disappearance of Emma Fault, the police sent us the suspect's pair of Timberland boots, and I was asked to examine them and to determine from the examination what type of soil that was and any vegetation within it, what clues that could give us to where that person had stood or had walked wearing those, those shoes, or boots in this case. Technologies and analytical methods are constantly evolving: ever smaller samples suffice for investigations. Microscopic soil residue on shoes can betray where a person has been.
Even tiny organisms can provide important information. At Frankfurt's Institute of Forensic Medicine, entomologist Jens Amendt works with some of them. In forensics, we use insects and especially flies to clarify questions about the victims' time of death. Because the traditional forensic procedures only work well one to two days after death. So in that window, you can estimate quite well when exactly the person died. But after that, there are no reliable forensic methods.
However, if insects have developed on the corpse, usually fly maggots, then we can use these to figure out the minimal amount of time the person has been dead for. The first step is to determine the species on the corpse. Then the developmental stage of each species is examined. Flies live on average about three weeks and within that time lay several hundred eggs. The maggots hatch after 12 to 25 hours. The larval and pupal stages each last about 10 days.
Normally, forensic entomology works relatively well to the exact day in the first three to four weeks after colonization. That's how long it takes for the adult fly to hatch, having passed through the egg, maggot and pupal stages; three to four weeks, approximately. And after that, accuracy is pretty much impossible. So we are hoping that the analysis, the chemical analysis of these empty puparia, will allow us to narrow down the time period beyond that point. Several weeks, several months, maybe even several years.
The pupal casing, the so-called puparia can offer further clues. In our forensic work we are trying to determine if the weathering of the puparia the shells that remain indefinitely intact at the site where the corpse was found if the weathering can be quantified. That’s where the cuticular hydrocarbons come in.
The shells contain specific hydrocarbon chains. We believe that over the course of time they break down, they decompose from long chains into increasingly shorter chains. So the analysis helps determine what hydrocarbon structures are actually still present in the cuticle we can reconstruct temporal processes, that is, we can work out: how long has this puparium actually been lying here at the site where the corpse was found? On the surface of all insects there are organic chemical compounds composed of carbon and hydrogen. Traces of these so-called cuticular hydrocarbons can also be found in the puparia and are analyzed in the gas chromatograph.
I believe that with the help of these puparia we can narrow down time periods that lie in the range of months or years. I’m hoping that we can say, for instance, this puparium is 2 to 2 ½ years old or this puparium is 8 weeks old. The research is still in the developmental stage, but Jens Amendt is confident that they will be able to apply the new analyses soon. What’s special about my work as a forensic entomologist is that I get to link basic research to its immediate implementation. So I can start an experiment to answer a fundamental question, and that answer in turn helps my work on cases at the institute, and provides the answers the police and prosecution need. For me, that's the biggest incentive and the fun of it.
It's exactly this spirit of innovation, curiosity, and broad scientific interest that is so indispensable in the forensic disciplines. Because often there is more than one way to solve a problem. To get results you have to use your imagination, be open for new perspectives, and always have one eye on the latest research developments. And what about the investigations into the eruption of mount Vesuvius? Were the ivy flowers Martina Weber found THE evidence for a later eruption date? We found it in the 2 children's skulls, but not in the adult; there was a single pollen grain there I think, and not in the reference sample either, there was significantly less there than in the children's noses. And yes, then you have to think, what do I do with it now with these results? And with Hedera, there are two problems.
One is just that, that it was only found in the children's skulls. The second is that Hedera Helix, the ivy, is an insect-pollinated plant so its pollen doesn’t just fly around on its own which means that the pollen must have somehow actively entered the nostrils. The explanation in the end was that in Pompeii's time the flower buds were preserved in oil or wine and a medicine was produced from it, which was dripped into the noses of children with respiratory problems. Suddenly our pollen spectrum was making a lot of sense: there was pollen in the children's skulls, not in the adults, and also significantly less in the reference sample.
So for the time being, the eruption of Vesuvius in 79 CE remains dated to August 24th. It is not enough to find the traces, they must also be considered in an interdisciplinary way. Because without the knowledge that at that time the pollen was also processed in other substances, the ivy trace would have led to false interpretations.
For Martina Weber, this was an interesting excursion into history, but it is time to return to the present. The clarification of the Höllental case in Austria is making slow progress. We’ve worked with Martina Weber on a number of cases in the past, and in this case too, where we didn’t know where the crime was committed, we started by doing a pollen examination on the items found with the body the blanket, for example and the victim’s shoes the idea being to determine which region or where these items could have come from. And Martina Weber from the University of Vienna has already helped us with some cases in the past; based on the pollen structure, she could tell the broad region the individual came from, or was staying in, and what distinctive flowers, plants, trees would be found growing in that area. What will the pollen trace analysis from the roadside body’s blanket reveal? Another tool for revealing and understanding evidence is bloodstain pattern analysis.
It is used in investigations especially when blood stains found at crime scenes do not match the suspect’s version of events. So of course in crime scenes where there's a lot of blood, we will focus on the bloodstains. The perpetrators will often say, ‘I only hit once’ or ‘in the heat of the moment’ or whatever a crime of passion.
And the bloodstain pattern shows a completely different story, a different picture. It means that we can disprove that it was one blow that fell in the heat of the moment, because in reality there were 15 blows, and they were not from the front, but from behind. So blood stain analysis can tell us a lot about the nature of the crime by the blood stain pattern. The French Mediterranean metropolis of Marseille is the location of a forensic laboratory run by one of the most innovative experts in blood stains Philippe Esperança. People from all over France, and other countries too, call on his expertise. The analysis of blood stain patterns can provide important information for crime reconstruction.
By examining and interpreting distribution patterns, forensic scientists can estimate the location, type and intensity of violent actions. The analysis of blood stains is based on the description of what you see. And that’s primarily the shape, the size, and the dispersion of the blood stains: that is, where they are found, their location the different surfaces they are found on; and their distribution: how are they arranged in relation to one another; are they convergent? Are they distributed in a linear pattern? These are the four principal aspects in identifying bloodstain patterns. There are luminol-based chemical agents that can detect traces of blood that has been wiped away.
When applied to surfaces that have had blood on them, the iron in the blood acts as a catalyst for the oxidation reaction. In the dark, the bloodstain glows blue and can be photographically documented. Conventional agents, however, destroy the DNA in the stains. Philippe Esperança has developed a recipe to preserves the blood’s DNA.
His reagent Bluestar is applied in a case in Nancy. A man is suspected of having killed his girlfriend. While searching his apartment, the police found traces of blood in the bathroom and the bedroom. The boyfriend had wiped it away. But he wasn't thorough enough, it turned out, once Philippe Esperança began his work. Looking at the photos he was sent of the alleged crime scene, he found an interesting pattern of stains on the wall in the bedroom.
Over here, we can see the mattress and the nightstand. And behind them on the wall, we can see patterns, little dot-shaped ones, some bigger, some smaller, but they aren’t those massive stains in which you can recognise the sponge or mop traces. And this is where it gets interesting. Because while all other traces have clearly been cleaned up, these ones have not. So I drove to the suspect’s house to have a closer look at that wall.
I found many stains that had not been cleaned up at all, because they were so tiny and on a dark surface, barely visible at all. One would have to actively look to notice them. Using Bluestar, though, we could see them all. Traces that have not been wiped away show the actual distribution pattern of blood during a crime even better.
Upon analysing the stains, we realized that they all converged to a point directly over this mattress. Therefore, there must have been some kind of blow that caused a wound. The impact caused the blood from the wound to spray in all directions, originating from that one point.
We’re talking about a convergent distribution. This is the type of pattern I found on the wall. But after the first or second blow, blood will also stick to the weapon, and when you move that, centrifugal force will create a more scattered pattern. In this case, blood isn’t distributed convergently, but follows the weapon’s movements. Imagine having water on your hand and moving it like this then water will fly away from your hand and distribute itself in accordance with the centrifugal force.
So you can follow the movement by looking at the drops on the wall. So we have the same shape, and, within the range of a few millimetres, same size of the traces, some oval, some circular. On impact, their distribution is convergent, whereas by movement, it is linear. And that's exactly what we had between the bed and the door.
In this case Esperança's analysis provides the necessary proof. In this case we used Bluestar. Firstly to confirm that the cleaning in question was actually the cleaning of blood and secondly that the blood belonged to the missing lady. These are the questions that need answering in such a case. So the gentleman is cleaning, but what is he cleaning? In the meantime all the French police services use Bluestar exclusively.
The other luminol-based products are no longer used. Today a genetic analysis is systematically carried out on all stains. The positive test for blood is not the end of the investigation a DNA test automatically follows.
It is unambiguously the missing nurse’s blood. The bloodstain pattern suggests that the victim was beaten while lying on the mattress. The blood spatter distribution leads Esperança to conclude that whoever did the beating must have been standing over the victim between the bed and the entrance door to the room. Combined with other evidence, Esperança's investigation leads to the conviction of the perpetrator.
The expert can be satisfied with his work for now. But there is room for improvement in forensic methods. One question in particular concerns him: The question of ‘when’. ‘You found my client’s fingerprint, their genetic fingerprint? Yes, but who’s to say it wasn’t there before the fact?’ So to link evidence to the crime, the question we now have to answer is: since when has this particular stain been on the instrument? On what day was it left? On the exact day of the crime and not a month before or after? Who knows for sure? Worldwide, there are several teams focussing on this issue we have to find a solution. International collaboration among forensic scientists plays an important role in solving crimes and making life safer in the process.
At the James Hutton Institute in Aberdeen, Scotland, Lorna Dawson works on the Galloway Forest case. The soil sample from the suspect's shoe was already in the lab for testing. As were other samples that had since been retrieved.
Some were recovered from the suspect's car. Lorna Dawson was able to compare them with the reference samples. In Scotland soil forensics is an integral part of investigations, but that’s not yet standard, internationally. Increasingly, all over, certainly Great Britain it is used, and it's considered to be used by the investigating authorities.
And overseas, there are more countries now considering adopting soil forensics within their portfolio of methods that can be used. A few years ago, I trained up some students from Brazil and they then went back to their own country and now they've set up a soil forensic lab. So it's really nice to see that this transfer of knowledge from one nation to another.
To get the clearest possible picture when analyzing soil samples, several different aspects are considered. If the samples from the suspect and those from the location where the body was found have the same origin, it’s an indication that the suspect was at that location. The soil sample are primarily tested for two compounds: Alkanes and alcohols.
So when we look at soils and compare soils from a questioned item and from a crime scene, let's see, we extract the carbon compounds. The compounds that we look at primarily are alkanes and alcohols. Here we've got a trace of the Alchin profile, alkanes being compounds that are composed of both carbon and hydrogen. And here we can see, for example, C 27.
That means twenty seven carbon atoms in that molecule. And the blue trace, the upper line here, that blue trace is from the sample that came from the footwear. The yellow green trace beneath it is the sample that came from the crime scene adjacent to where the victim's body was found. And as you can see, the retention time on the gas chromatograph, you can see at C 27 and C 29, C 31 and C 33, the peaks are there in the same place, the same compound, and the height of these peaks of the same.
So from that we can conclude that there is the same profile with the same amounts and the same relative amount of the different carbon compounds in the question sample and a sample that was recovered from the crime scene. So the samples from where the body was found match those from the soles of the suspect's shoes. The suspect can now be clearly linked to the secondary crime scene. It is suspected that he dumped the body there, walked away from the site, got into his car and drove away.
Lorna Dawson presented her findings on the woman’s murder case at court. Her expert opinion and those from other areas led to the perpetrator's conviction. Often forensic experts don't learn the full circumstances of a case until after the investigation is complete. Although we stay objective and try not to get involved at all in the actual crime itself in terms of the families involved that's not the duty or the rule of any forensic scientist. But one always has to have compassion, and confidentiality is absolutely key. But once a case has been tried and you then are aware more fully of the whole case circumstances, it really does hit home the need, the need to provide as much evidence, objective evidence that can help that court make the right decision and bring some closure for the families that are involved in these sometimes very difficult situations, but equally well to also produce evidence that avoids a situation where someone is falsely accused of a crime.
So that's why it's important that the evidence stands on its own and is available to both prosecution and defense. But the use of soil analysis is not limited to crimes against humans. It can, of course, also help to uncover environmental crimes.
Or to relate agricultural performance to soil biological properties. And also to assess climate change, identify hazards of soil erosion and compaction, and much more. In the past, biology and botany-related research fields did not have much of a say in forensic science.
However, with evolving technologies and methods, more and more natural science disciplines are being used in forensics. DNA analyses are now commonplace. But interdisciplinary thinking and structural networking are also fundamental.
Martina Weber has a unique digital collection of pollen grains. In order to unambiguously identify pollen from all over the world, she and her colleagues at the botanical institute of the University of Vienna are building an internationally accessible pollen database: "PalDat". It is the world's largest palynological database. Weber's goal is to make the entire data collection from multitudes of plant families publicly accessible. Each of us had umpteen pollen data in the various rooms, and originally we just wanted a database that we could use to share info with each other. But pretty soon the world, so to speak, was crying out for more a free database, so we set that up and put it online.
It really only makes sense if you work together. If everyone sits on their own data, then no one benefits. Almost 4500 plant species and their pollen are already cataloged in the database. In the case of the Höllental victim in the blanket, the pollen provides clear clues. Most criminals won’t even be conscious of leaving the kind of traces that Martina Weber is working with. After a few weeks, due to a confidential tip, we received information on the individual’s acquaintances and on a possible suspect or several suspects.
We then started to investigate or monitor these persons. The police have three suspects in sight and suspect that the crime took place in one of their apartments. But how can they prove the crime? Or prove that the victim was even present at the suspected crime scene? At the very bottom, we can see the sample from the crime scene. This was an attic in a detached house. And you can see, we find precisely these plants again and again in large quantities.
So this brown bar, these are cypress trees; you can imagine cedars and the like, which is very popular in hedgerows in Austria. There was willow in the garden, and poplar, also asters and a variety of other plants, dandelions and the like. There is no doubt at all that these pollen grains came from the primary crime scene. And when we also found it on the victim’s shoe, we could say for certain that the victim actively made his way to the crime scene. And also that the perpetrators wrapped him up at the crime scene.
The pollen diagrams of the traces from the house and from the blanket paint a clear picture. Martina Weber was able to prove that the trace patterns from the woollen blanket and the suspect's attic matched. Lead Investigator Hannes Fellner very much appreciates the cooperation with the scientists and wishes to create stronger networks, both nationally and internationally. We cooperate with as many experts as possible in the field of forensics.
We are open to all kinds of investigations. We are really trying to link up internationally and are always on the lookout for new contacts, because of course there are different kinds of expertise in other countries the police have different experiences so when the case requires it, we can fall back on these experts. And that’s only possible through international networking. It doesn't really work any other way.
Palynologist Martina Weber will continue to develop the legacy of her predecessor. It will continue on all levels I think; especially with pollen as there is still an awful lot of potential, even with cold cases. Because the pollen, no matter in what form whether you have somehow retrieved a pollen grain or whether you have a piece of clothing or a strand of hair from the corpse the pollen doesn’t decay. So as long as it doesn’t go moldy, the pollen will be wonderfully preserved.
It means we can always isolate pollen from any material, whether it’s 50 years old or 100 years old, and when appropriate use it to draw conclusions. Current research developments make it look as though no crime can remain unsolved in the future the search for evidence is too sophisticated, too advanced and high-tech, and so too are the methods researchers use to analyze the traces. But with all these advancements, one thing shouldn’t be overlooked: most of this high-tech would be redundant without the materials provided by nature.
2022-09-27