Jonathan Toebbe (right) and his wife, Diana Toebbe, are shown in booking photos released October 9, 2021.
Washington CNN  — 

US Navy nuclear engineer Jonathan Toebbe pleaded guilty to one felony count in federal court Monday afternoon, four months after he and his wife were arrested and charged with trying to sell classified information about nuclear submarines to a foreign country in exchange for millions of dollars of cryptocurrency.

Toebbe, 43, will face between 12 and 18 years in prison, according to the plea agreement read aloud by prosecutors in a federal courtroom in Martinsburg, West Virginia. He was initially charged with three federal felonies, each carrying up to life in prison.

Federal Magistrate Judge Robert Trumble accepted Toebbe’s guilty plea and another federal judge will sentence him at a later date. That judge will have the option to impose a different sentence than agreed upon by Toebbe and prosecutors.

Toebbe will remain in jail until his sentencing date, which has not yet been set.

In court Monday, Toebbe admitted that he had “conspired with Diana Toebbe,” his wife, “to transfer restricted data to a foreign country” with “the intent to injure the United States.” Diana Toebbe, who remains in jail, has also been charged with three federal felony counts. She has pleaded not guilty.

Diana Toebbe has repeatedly tried to get released on bond, saying she did not know about her husband’s plans, though she accompanied him to several dead-drops.

Jonathan Toebbe has also agreed to cooperate with prosecutors, according to the plea details, and has pledged to return the $100,000 in Monero cryptocurrency paid to him by the FBI during the investigation.

Toebbe first sent a package to an undisclosed foreign government in April 2020 offering to sell nuclear secrets, and that government turned over the offer letter to the FBI, according to the criminal complaint.

An FBI agent responded to Toebbe several months later and corresponded with him, eventually entering into an agreement with Toebbe to exchange thousands of dollars in cryptocurrency for the nuclear secrets.

Toebbe and his wife are accused of acting together to coordinate three separate drop-offs of SD cards containing classified information about nuclear submarines, specifically the Virginia-class submarine.

The couple allegedly went to great lengths to hide the SD cards at the dead-drop locations over the course of several months, tucking an SD card into a saran-wrapped peanut butter sandwich in one instance, while others were hidden inside a packet of gum and a sealed Band-Aid wrapper.

FBI agents were monitoring and surveilling the Toebbes for months until they were eventually arrested on October 9 at what was to be their fourth dead-drop location.

At an October court hearing, prosecutors revealed that the government had still been unable to locate most of the classified data allegedly stolen by Jonathan Toebbe, warning that the information could cause extreme damage to the Navy if it were got out.

As part of Toebbe’s plea agreement, he has agreed to cooperate with government investigators – allowing them access to his electronic devices and accounts – and will also assist federal officials to find all of the classified information he allegedly stole from the US Navy.