Soldiers of the 23rd Weapons of Mass Destruction Civil Support Team decontaminate their protective suits after sweeping the area utilizing special biological and chemical detectors in response to a possible biological threat during a training exercise at the David C. Canegata Recreational Center and Sports Complex on Sept. 25, 2019. (U.S. Army National Guard photo by Army Staff Sgt. Gregory Camacho)

Tracing the Source of Chemical Weapons

The forensic chemical attribution process seeks to trace chemical agents used in attacks. Investigators take a sample of the agent from a victim or site, and then analyze its physical and chemical properties. The data can be used to identify a “chemical fingerprint,” which could provide information to investigators about how the agent was made.

Investigators could use this data to match and trace the agent to its source to help find and prosecute attackers, impose sanctions, or deter future attacks. The Government Accountability Office explored the opportunities and challenges to implementing the forensic chemical attribution process.

Some governments are suspected of using chemical weapons despite international prohibitions under the Chemical Weapons Convention. For example, sarin and VX nerve gas have been identified in attacks. Most recently, Novichok nerve agent was used in 2020. Technologies exist to identify chemical warfare agents and possibly their sources, but challenges remain in identifying the person or entity responsible.

According to the Global Public Policy Institute, there have been more than 330 chemical weapons attacks since 2012. Such attacks are prohibited under the Chemical Weapons Convention. A set of methods called forensic chemical attribution has the potential to trace the chemical agent used in such attacks to a source. A set of methods called forensic chemical attribution has the potential to trace the chemical agent used in such attacks to a source. For example, investigators could use these methods to identify the geographic sources of raw materials used to make the agent, for example, or to identify the manufacturing process Such information can aid leaders in deciding on whether or how to respond to a chemical weapons attack.

Forensic chemical attribution is a three-step process, though the third step is being developed. First, a sample is taken from a victim or the site of an attack. Second, the sample’s chemical components are analyzed and identified, either at a mobile lab or at one of 18 authorized biomedical labs worldwide. Common identification methods are:

  • Gas chromatography, which separates chemical components of a mixture and quantifies the amount of each chemical.
  • Mass spectrometry, which measures the mass-to-charge ratio of ions (i.e., charged particles) by converting molecules to ions and separating the ions based on their molecular weight.
  • Nuclear magnetic resonance (NMR), which can determine the structure of a molecule by measuring the interaction between atomic nuclei placed in a magnetic field and exposing it to radio waves. NMR works on is the same principle as magnetic resonance imaging (MRI) used in medical diagnostics.

In the third step—still under development—investigators use the data from the forensic chemical identification and analysis and identification methods from step two to develop a “chemical fingerprint.” The fingerprint can be matched to a database of information on existing methods or known sources to identify chemical agents. However, a comprehensive database containing complete, reliable data for known agents does not exist.

Forensic chemical analysis and identification is mature for known chemical agents. For example, investigators determined the nerve agent sarin was used in an attack on civilians in 2017. The methods can also identify new agents, as when investigators determined the chemical composition of the Novichok nerve agent after its first known use, in 2018.

Forensic chemical analysis and identification methods are also mature enough to generate data that investigators could use as a “chemical fingerprint”– that is, a unique chemical signature that could be used in part to attribute a chemical weapon to a person or entity. For example, combining gas chromatography and mass spectrometry can provide reliable information about the chemical components and molecular weight of an agent. To achieve Step 3, scientists could use this these methods in a laboratory experiment to match impurities in chemical feedstocks of the weapon to potentially determine who made it. In an investigation, such impurities could indicate the geographic origin of the starting material and the process used to create the agent.

Read the GAO report

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