Chemical warfare agent forensics: why is it so slow?
Investigations of alleged use of illegal chemical warfare agent use are painstakingly slow, and this leads at times to criticism. Why does it take days to search a house? Why can it take weeks for results to come back from a laboratory? For the most part, people derive their understanding of forensic sciences from films and television, neither of which provide an accurate picture of reality. The purpose of this particular article is to describe what chemical warfare forensics is really about, whether it involves Syria or Salisbury.
When confronted with a crime involving a chemical warfare agent (or biological or radiological ones, although this article focuses on chemicals) proper forensic processes are necessary for a number of reasons. The identity of the materials used may be necessary for safety and health. The identity of the attackers is important, so that they can arrested and prosecuted. Future events can be deterred or prevented. The way evidence is collected, analysed, and preserved is very important.
Legal proceedings in national and international courts rely on evidence. With chemical warfare attacks the physical evidence is extremely important. In any trial, defence counsel in trials and hearings will challenge any evidence that has been presented. The whole chain of events involving the collection, processing, and storage of the evidence will be subject to challenge. Lawyers will question the evidence and everything to do with the evidence. Where did you collect the sample? How did you know that was where to look for a sample? What container did you use to collect it? Was it sterile? Can you prove it was sterile? What technique was used?
A competent forensic technician knows how to answer these questions from a hostile attorney. Defence counsel is not doing their job properly if they are not challenging the evidence that is being presented. All of this is just as relevant in normal criminal procedures as it is in a chemical situation. Botching the evidence could mean that the perpetrators go free. Clearly, such an environment and conditions call for precision and thoroughness. In order to explain exactly how and why this is the case, it is easiest to divide up the business into three parts.
The Front End: Identifying and collecting materials
What I refer to as the ‘front end’ is all of the work that goes on to collect materials at the incident scenes. The incident scene needs to be defined, segregated, and protected. Technicians will need to collect chemical evidence, which takes many forms, such as solid, liquid, gas/vapour, surface swabs, soil samples, and biomedical evidence, all of which require a variety of specialised techniques and equipment. It may not be obvious where the chemical evidence is located, so a variety of detection and identification instruments will be used to locate relevant evidence. Evidence needs to be carefully collected in ways that do not spread the contamination. Things like tools and gloves need to be exchanged frequently in order to prevent cross-contamination. These discarded tools and gloves may have evidence on them and may also need to be processed as evidence. On one biological incident, I exchanged gloves perhaps 30 times in one morning. In addition, photographic and video recording of evidence collection is usually recommended.
Just because an incident is related to a chemical warfare agent, it does not remove the requirement to collect relevant conventional evidence, some of which may contaminated. Collecting conventional evidence in a potentially chemically contaminated environment may require speciality equipment and training. Tasks that might be simple in a normal crime scene, such as dusting for fingerprints, may be very difficult if you are wearing a gas-tight suit and breathing apparatus. Sometimes it may be easier to remove entire items, such as pieces of furniture or vehicles, than to expend precious hours swabbing every surface and cutting swatches out of them.
In most instances, the speed with which work can proceed at the scene of a chemical incident is greatly reduced compared to that at a conventional scene. Which is not fast to begin with. The health and safety of the evidence technicians means that technicians will be wearing personal protective equipment (PPE - UK guidance here and USA guidance here). Depending on both the nature of the threat substances and the often rigid health and safety regulations applicable, this can mean anything from a pair of gloves all the way up to gas-tight suits and self-contained breathing apparatus. Sometimes, health and safety rules and the associated risk assessment processes that give little latitude to managers on the scene will dictate a higher level of protection than actually needed, hence the scenes of technicians wearing sophisticated suits in Salisbury. Indeed, different agencies and different on-scene commanders may interpret their own checklists and procedures differently. People operating inside closed spaces, such as vehicles and buildings, may face a higher threat from vapours than those in open air. However, once the nature of the threat is characterised, on-scene commanders have more leeway to adjust PPE to the specifics of the scenario. For example, once a threat is known to only be a contact hazard, the primary PPE becomes suitable gloves and boots, not full gas-tight suits.
Operating in PPE has several implications. Staff need to be rotated due to factors like heat stress and air supply. Hot weather can reduce the number of minutes a person can spend in PPE. Not all of the evidence technicians may be qualified or able to work in full PPE, so the supply of personnel to do the work will be a controlling factor. Working in PPE causes many tasks to be executed more slowly. Exiting from a potentially contaminated incident scene will require decontamination, which must be factored in. Safety usually necessitates that a standby team be available in the same PPE in order to rescue or assist a team in the hot zone should they get into any sort of trouble. These factors necessitate careful planning of entries into chemical incident scenes. Compared to collecting evidence at a conventional incident, it could quite reasonably take five or ten times as much time in a chemical environment.
The Middle Bit: Storage, custody, and control measures
Evidence needs to go into containers, which must, in turn, keep the evidence safe. These containers, whether they are bags, bottles, jars, or tubes, all need to be sterile. And their sterility has to be certified, lest there be some question as to whether the evidence is tainted or cross-contamination has happened. If you cannot prove that the container you are using is sterile, it is not worth putting the evidence in it in the first place. Once contained, evidence must be accounted for and secured. There needs to be a “chain of custody” which is basically an audit trail stating where the evidence has been and who has been responsible for it. If there are periods of time where the evidence cannot be accounted for, it will be questioned at court and possibly disregarded.
Various control measures are needed in order to the prove the integrity of the whole process. There are a variety of negative control measures, such as blank samples. For example, if you put a number of samples into plastic bags, you also want to take one of the same plastic bags from the same lot, but not put anything in it, and submit it as a sample for evidence (more on blanks here). Negative samples will help prove the sterility of containers and the overall integrity of the process.
The Back End: The laboratory
Once items arrive in the laboratory, they need to be subjected to a variety of processes and procedures which are too complex and varied to be fully described here. Various factors and issues make this a laborious process. There’s very few labs that are allowed to handle chemical warfare agents. Many types of chemical evidence may need to be examined on multiple instruments. A backlog of samples is likely to build up as each sample needs to be examined with similar rigor. Some types of analytical processes could take a significant amount of time for a single substance. In addition, the threat of cross-contamination of instruments means that some laboratory instruments may need thorough cleaning between samples. Various analytical techniques are destructive, so a small sample of a liquid, for example, may need to be subdivided as some of the evidence will actually be destroyed during the laboratory phase of the operation.
Exploitation of conventional evidence in a chemical warfare agent laboratory environment can add a lot of time to an investigation. For example, processes for lifting fingerprint or DNA evidence from a container than held some nerve agent cannot be done in the normal criminological laboratory, for legal and safety reasons. These processes will have to occur in specialised conditions, which will add time to the overall effort. Safety and working conditions play an important role too. Overworking the laboratory technicians is a false economy if it leads to errors and unsafe acts, and is likely against regulations and laws. A laboratory only has a limited amount of trained labour available. Even a modest crime scene could produce many thousands of samples. Adhering to correct processes, it can take months for all of the evidence to be analysed.
The same control measures mentioned earlier are important in the laboratory stages. Blank samples can demonstrate that laboratory processes are inadequate, such as when a chemical of interest turns up in a known blank sterile sample. In laboratory processes, the concept of a positive control sample is also important. This is when a chemical of interest is deliberately introduced as an additional sample. The lab does not know which samples are from the field and which are the control samples as they are submitted all together. The positive control sample affirmatively shows that the laboratory knows what it is doing and can detect substances of interest. For example, in the Skripal investigation, the OPCW added samples containing a substance called 3Q (also known as BZ) to the samples from the field as a positive control measure.
Once the front, middle, and back ends of the operation are taken into consideration, forensic evaluation of a chemical warfare agent incident will take a great deal of time. Given the context of how these investigations work in the real world, questions like “how can it take a week to search a house” and “why did it take a month for the lab to analyse the samples and issue a report” are easily answered.
You want to know more?
People interested in the technical details of chemical warfare forensics are advised to look at the various books written by Steven Drielak, which are canonical references.