Poison, alcohol, drugs? The search for clues in the laboratory
In forensic toxicology, pharmacists search for foreign substances - and thus help to solve crimes
Gas station attendant or forensic toxicologist - the suggestions made by his advisor in the employment office sounded to the high school graduate Cornelius Hess as if she had simply typed the letter T in the vocational lexicon. From the forensic toxicologist, Hess didn't even know what he was doing.Perhaps the following job description would have convinced the young man at the time: "Drink, sex, violence and drugs - that's how we earn our money." This is what it says in the book "Mordgifte", written by two forensic toxicologists. One of them: Dr. Cornelius Hess.
Obviously, the career counselor did her job well. Since 2018, the now 37-year-old Heß, after studying pharmacy and a stopover in doping analysis at the Cologne Sports University, has been head of forensic toxicology at the Institute of Forensic Medicine at the University of Mainz. In milliliters of blood, in droplets of urine, in pencil-thick strands of hair, and sometimes in a few grams of brain or liver tissue, he looks for substances that do not naturally occur there.
The connection between cappuccino foam and cyanide murder
Basically, Hess is a kind of pharmacist in reverse: He does not recommend which active substance a patient should take in which dosage - he reconstructs what and how much someone has already taken. A very exciting job, thinks Hess. For whom else can the consistency of the cappuccino foam from the office machine be more than a morning nuisance? Maybe the last missing piece of information for a cyanide murder? Just.
Most of the cases forensic toxicology deal with revolve around blood alcohol, drug, and medication evidence. The aim is to determine for investigative authorities such as the police, public prosecutor's office or the courts whether someone has committed a crime under the influence of so-called foreign substances, for example driven drunk or stoned. Or whether someone is really abstinent after such a crime and can now get his driver's license back. Some facilities also work closely with clinics and examine samples from acute emergencies. If a child is admitted with symptoms of intoxication, the toxicologists can determine what the little patient has swallowed - so that the doctors act accordingly.
20,000 autopsies per year
Body fluids from deceased people end up in Mainz almost every day at Hess and his team. Corpse toxicology is also one of the tasks of forensic medicine institutes. If there is a suspicion that a person did not die naturally, the public prosecutor orders an autopsy. According to the Society for Forensic Medicine (DGRM), 20,000 of these are carried out in Germany every year.
Many experts believe that too little. In particular, poisoning would often not be detected in a normal post-mortem examination, for example if a heart disease was instead suspected as the cause of death. The DGRM assumes that for every homicide there is an undetected one. And this estimate is still conservative.
Various professional groups work hand in hand to ensure that a corpse reveals its secrets. Two doctors open the body at the dissection table and check, among other things, whether the person was subjected to violence before he died: Does the skin have injuries such as punctures, cuts, crusts? Have hematomas formed in the tissue? Are the bones intact or broken? In addition, it is examined whether the organs were functional to the end and whether something speaks for an undiscovered disease, an addiction or a poisoning.
Dr. Cornelius Heß, Forensic Toxicology of the Institute of Legal Medicine, University of Mainz
© JGU press photo
Solid and liquid samples are preserved at minus 19 degrees
In about half of the 500 deaths in Rhineland-Palatinate each year, the cause of which is unclear and therefore ends up in the Mainz forensic medicine department, the public prosecutor commissioned a chemical-toxicological investigation. For example, when the investigation file says that an empty pack of Schlaft  tablets was found at the place where the corpse was found.
Because such an examination can only be commissioned weeks or years later, the doctors not only cut open the dead body, but also always cut off tiny pieces. In addition to blood and urine, they also secure organ material and the stomach contents of the corpse for their colleagues in toxicology, which are then pureed.
All these solid and liquid samples are placed in small glass vessels and move two floors higher to the laboratory of the team around Cornelius Hess. There they are processed and stored at minus 19 degrees until analysis so that the material remains stable for longer.
The search for clues then continues at the molecular level. "Basically, the toxicological analysis is like a puzzle. The overall picture is slowly being put together from individual parts," says Dr. Marc Bartel, Head of Forensic Toxicology at the Institute for Forensic and Traffic Medicine at Heidelberg University Hospital. It's actually like US crime series like CSI - just not quite as futuristic and fast.
Blood is the number one test material
If there is no clear indication of a certain substance such as sleeping pills or drugs on the basis of the investigation file, the experts systematically search for a wide variety of substance groups. They call it "General Unknown Screening". Thanks to individual molecular structures, each chemical substance has its own fingerprint. 10,000 such fingerprints are stored in toxicological databases.
If the experts can identify one of them in a blood sample, it is analyzed in more detail in a second round. After all, the result of the detective work must be usable in court.
Blood is the test material of choice. Substances can usually be detected in it for several hours. Experts can deduce the concentration and from this, in turn, how strongly something must have had an effect - and whether it was present in lethal quantities. Analyzes of the urine, on the other hand, can often only prove that a substance has been absorbed. The substances themselves or their metabolic products can usually be found in the urine for several days - in order to be able to excrete foreign substances, the body often converts them so that they are water-soluble. But they are much more concentrated there than in the blood. And the individual drinking amount can falsify the result.
Crucial indications for charge and sentence
Some substances are also deposited in the hair. The advantage of a toxicological analysis on this basis: Depending on the length of the hair, consumption can be detected that was months or even years ago. Since a hair on average grows one centimeter per month, the time and duration of consumption can even be determined relatively precisely afterwards. In this way, for example, the truth about his cocaine abuse came to light with soccer coach Christoph Daum.
Using hair analysis, the toxicologists can also help the investigating authorities if they suspect knockout drops. For example in this earlier case by Cornelius Hess: A man had drugged his niece with so-called gamma-hydroxybutyric acid and then abused it. The girl suffocated. Hess and his team were able to prove that the perpetrator had repeatedly given his victim the drug over a period of several months. From this it could be concluded that the abuse had presumably occurred several times - a crucial indicator for the prosecution and the sentence.
Even murder poisons are fashionable
Knockout drugs, sleeping pills or sedatives are now common substances in the context of violent crimes or suicide. What intentionally or unintentionally intoxicated or poisoned with has always been dependent on two things: the availability and the state of the art. Substances that are difficult to track down are generally used - and thus also the crime.
Compounds of the semi-metal arsenic were a very popular murder poison from the Renaissance to the 19th century. Until the English chemist James Marsh was able to prove the substance for the first time in 1836. At the beginning of the 20th century, many synthetically produced painkillers such as opiates came onto the market, and chemical drugs were experimented with in laboratories. Both opened up new opportunities for abuse.
During the Nazi era, cyanide gained notoriety: the active ingredient in the pesticide Zyklon B was used as a means of mass destruction by the Nazis - whose grandees, ironically, sometimes killed themselves with cyanide capsules when the defeat of the Germans became apparent.
Fates depend on careful toxicological analyzes
Hess and his colleague describe a very rare, more recent cyanide case in their book: that of the "cappuccino killer" mentioned above. It caused a stir in the early 1990s. The operations manager of a Lüdenscheid company for surface finishing had enriched himself with gold-containing production waste. When his deputy became suspicious, he added sodium cyanide - also used in manufacturing processes - to a cappuccino and offered it to her. After just one sip, the woman convulsed, collapsed, and died of acute poisoning.
Investigators soon identified the triggering substance, but now it was time to check whether the dead woman had killed herself, as the operations manager claimed? Or had he given her the poison in the cappuccino that was offered unnoticed? Since suicide seemed unrealistic, a toxicologist on site checked how well cyanide dissolves in the company's coffee machine. The result: not even the head of foam disappeared. This and other evidence reinforced the suspicion against the operations manager, who was ultimately sentenced to life imprisonment for murder.
Human fates depend on his careful toxicological analyzes and their interpretation - Cornelius Hess is constantly aware of this. At the latest in court, his rehearsals get faces and stories. The work of pharmacists like him, but also of biologists, chemists or food chemists in forensic toxicology, includes laboratory analyzes, research and teaching as well as writing reports and presenting them as experts in processes.
Sometimes Cornelius Heß asks witnesses and defendants the last question. The judges then withdraw to announce their verdict a little later.