Late last year, Mr. Tereshchuk was sentenced to five years in prison after pleading guilty to a criminal extortion charge filed by the United States attorney's office in Alexandria. Earlier this year he pleaded guilty to criminal possession of explosives and biological weapons, charges that the United States attorney's office in Baltimore had filed against him. Possessing illegal toxins carries a maximum term of life in prison. Mr. Tereshchuk is expected to be sentenced this fall.