SPOKANE — A Spokane man charged with mailing a poison-laced letter to President Obama pleaded not guilty to three charges Wednesday in federal court.

Matthew Buquet, 37, entered not-guilty pleas during an appearance before U.S. Magistrate Cynthia Imbrogno.

He is charged with producing and transferring a biological toxin called ricin; mailing a threatening communication to the president of the United States; and mailing a threatening communication to a federal judge. He faces up to life in prison if convicted.

The FBI has said Buquet mailed five ricin-laced letters to various federal entities. He was arrested last month. All the letters have been recovered and there were no reports of injuries.

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No motive has been offered for the mailings, and the federal government has sealed most of the court documents in the case.

Little is known about Buquet, who has made no statements in court other than “yes” or “no” answers to questions from the magistrate. He appeared in court Wednesday with a long black beard, dark-tinted glasses and wearing shackles.