A Missouri man was sentenced today to 12 years in prison after he attempted to buy a deadly poisonous chemical from the dark web during an undercover FBI operation.

The suspect, a 46-year-old man named Jason William Siesser of Columbia, Missouri, was also denied parole due to the severity of his crime.

According to the US Department of Justice, Siesser tried on two occasions to buy dangerous chemicals classified as “chemical weapons” by US authorities from a seller active on the dark web.

While an initial attempt in June 2018 failed, Siesser completed a sale in August 2018 and had the chemical delivered to his home under the name of a minor he was legally fostering.

According to insufficiently redacted court documents obtained by The Record, Siesser bought three vials of dimethylmercury from a dark web broker, for which he paid $150 in Bitcoin.

Dimenthylmercury is an organic form of mercury and one of the deadliest neurotoxins on Earth, which can poison humans even in small quantities, either by ingestion, inhalation, or even the smallest skin contact.

The FBI said that the three dimethylmercury vials had the capacity to kill up to 300 people. Death from dimethylmercury is a slow and agonizing process that can last from weeks to months.

Suspect received “not dimethylmercury”

But officials said that Siesser never had the dimethylmercury in his possession. On the day of the delivery, he received an inert substance described by the FBI as “not dimethylmercury,” and was arrested 30 minutes later.

FBI agents who searched Siesser’s house after the arrest said they found writings in the suspect’s home expressing heartache, anger, and resentment over a breakup, along with statements suggesting Siesser might intend to harm or murder the former lover. Court documents did not make it clear if Siesser referred to his former wife or a former date.

In interviews Siesser gave FBI agents after the arrest, he acknowledged that he did not have a permit to possess the neurotoxin and that he knew dimethylmercury was a deadly substance after he “read an article about a scientist who died after being exposed to dimethylmercury.”

Siesser was most likely referring to the death of Dartmouth College professor Karen Wetterhahn in 1997.

Siesser’s arrest and sentencing is a rare case where a suspect was caught trying to buy what classifies as a “chemical weapon” on the dark web, a place where listings for malware, drugs, weapons, and fake documents are more common. A Canadian woman was sentenced in a similar case in June 2020 to six years in prison after she also tried to buy what authorities described as a “toxin.”

Header image via Steven BraceCC BY 2.0


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Catalin Cimpanu is a cybersecurity reporter for The Record. He previously worked at ZDNet and Bleeping Computer, where he became a well-known name in the industry for his constant scoops on new vulnerabilities, cyberattacks, and law enforcement actions against hackers.

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