Ilya Lichtenstein, the mastermind behind the multi-billion dollar hack of cryptocurrency exchange Bitfinex, has testified in a Washington, D.C., trial, revealing the intricacies of one of the largest Bitcoin heists in history.

Lichtenstein, who appeared as a cooperating witness in a money laundering trial, disclosed that he had access to Bitfinex’s systems for several months, allowing him to execute the hack. He also admitted to hacking into individual accounts at other crypto exchanges, including Coinbase and Kraken.

The hacker, along with his wife, Heather “Razzlekhan” Morgan, pleaded guilty last year to a money laundering conspiracy connected to the Bitfinex hack. Lichtenstein’s testimony included details about his use of mixing services, such as Bitcoin Fog, to hide laundered assets from the hack. He noted that while Bitcoin Fog was one of the mixers he used, it wasn’t his primary method of laundering, and he moved on to other services that better suited his purposes.

The trial also involves Roman Sterlingov, the accused operator of Bitcoin Fog, who is facing charges of money laundering. Lichtenstein’s cooperation with federal prosecutors is part of his plea agreement, which could see him sentenced to a maximum of 20 years in prison.

Heather Morgan, known as an aspiring rapper, faces a maximum possible sentence of five years in prison. The couple’s arrests in February 2022 led to the seizure of over 94,000 bitcoin, valued at approximately $3.6 billion at the time, making it the largest seizure in DOJ history. The DOJ has since seized an additional $475 million tied to the hack.

The revelation of Lichtenstein’s involvement in the Bitfinex hack comes after years of speculation, with the value of the stolen bitcoin soaring from $70 million at the time of the theft to $4.5 billion. The couple’s story has garnered attention, with Netflix commissioning a series on their exploits.