Washington, D.C. — An Ohio resident was sentenced to three years in federal prison for his role in operating a darknet cryptocurrency “mixer” that laundered over $300 million in bitcoin, authorities announced Friday. Larry Dean Harmon, 41, of Akron, was the mastermind behind Helix, a service that helped obscure the origins of cryptocurrency transactions tied to illegal darknet activities from 2014 to 2017.
According to court documents, Harmon ran Helix in conjunction with Grams, a darknet search engine he also controlled. Helix became a widely-used tool among darknet drug traffickers seeking to launder profits. The mixer processed at least 354,468 bitcoin — worth approximately $311 million at the time — funneling transactions to and from darknet markets, including some within the District of Columbia.
“Harmon’s operation provided a service that specifically catered to criminals looking to hide their illegal proceeds,” said U.S. Attorney Matthew M. Graves for the District of Columbia.
“This sentencing sends a strong message that the anonymity of the darknet does not shield wrongdoers from justice.”
As part of the sentence, Harmon will also serve three years of supervised release following his prison term. In addition, he is required to forfeit assets exceeding $400 million, including cryptocurrencies, real estate, and other financial holdings.
“This case underscores the Justice Department’s commitment to tracking and dismantling complex cybercrime operations, no matter how deeply hidden,” said Nicole M. Argentieri, Principal Deputy Assistant Attorney General and head of the Justice Department’s Criminal Division.
Helix’s integration with Grams allowed it to be easily accessible to darknet markets, facilitating seamless bitcoin withdrawals. Harmon created a special Application Program Interface (API) for Helix, which enabled darknet platforms to directly connect to the mixer. He further modified Helix to ensure compatibility with several prominent illegal markets, enhancing its popularity and usage.
Investigators managed to trace tens of millions of dollars worth of illicit transactions from major darknet platforms back to Helix. Harmon admitted to earning a percentage from these transactions as fees, acknowledging his role in a conspiracy to launder money.
In August 2021, Harmon pleaded guilty to conspiracy to commit money laundering, and his sentencing has now brought closure to one of the most significant cybercrime cases involving cryptocurrency. Beyond the $311 million forfeiture money judgment, additional assets — including bitcoin and other cryptocurrencies seized during the investigation — were valued at over $400 million.
Key agencies involved in the case included IRS Criminal Investigation (IRS-CI), the FBI’s Washington Field Office, and the Justice Department’s Office of International Affairs. International cooperation played a crucial role, with significant assistance from Belize’s Attorney General’s Ministry and Police Department, coordinated through the U.S. Embassy in Belmopan.
“The scale of this operation illustrates the evolving landscape of digital financial crime,” said Chief Guy Ficco of IRS Criminal Investigation.
“We will continue to target those who attempt to exploit cryptocurrency systems for illicit purposes.”
In a parallel civil case, the Financial Crimes Enforcement Network (FinCEN) imposed a $60 million penalty on Harmon for violating anti-money laundering regulations, a penalty that highlighted the seriousness of the charges against him.
The prosecution of the case involved experts from the Justice Department’s Computer Crime and Intellectual Property Section, along with key personnel from the District of Columbia and Northern District of Ohio U.S. Attorney’s Offices.
“Our success in this case is a testament to the power of international and interagency cooperation,” said Bryan Vorndran, Assistant Director of the FBI’s Cyber Division.
“We will continue to pursue those who misuse digital currency platforms to facilitate illegal activities.”
