Prosecutors say that Manafort directed a large scale lobbying operation in the U.S. for Ukrainian interests without registering with the Justice Department as required by the federal Foreign Agents Registration Act, or FARA. Manafort was accused of concealing from the IRS tens of millions of dollars in proceeds from his Ukrainian patrons and conspiring to launder that money through offshore accounts in Cyprus and elsewhere.

READ MORE: Another trial looms for ex Trump campaign chairman Manafort

Manafort had denied the allegations and pleaded not guilty. Even after his indictment last October, though, prosecutors say he continued to commit crimes by tampering with witnesses. The discovery of his witness contacts led to a superseding indictment in June and Manafort’s jailing ahead of his trial.

In addition to the witness tampering counts, Manafort had been formally charged with acting as an unregistered foreign agent, conspiring to launder money and lying to the FBI and Justice Department about the nature of his work. Court papers filed in the case indicated that he could have faced between 15 and 19 1/2 years in prison under federal guidelines.

The charges do not relate to Russian interference in the 2016 presidential election.

WATCH: How convictions of Manafort, Cohen compare to Watergate