Shannon Richardson/via Flickr Creative Commons

Shannon Richardson, a former actress from Texas, pleaded guilty on Tuesday in federal court to sending poisoned letters to President Barack Obama and New York Mayor Michael Bloomberg.

Richardson, 35, faces up to 18 years in prison for sending three ricin-laced letters to Obama, Bloomberg, and the director of Bloomberg's anti-gun group Mark Glaze, earlier in the year.

Prosecutors said that Richardson had mailed the ricin letters in an attempt to frame her estranged husband on May 20, 2013. During the FBI investigation, Richardson made inconsistent statements to authorities and failed a lie detector test. She was arrested by the FBI and charged in June.

Richardson has had minor roles in television series, including "The Walking Dead" and "The Vampire Diaries." She also had a minor role in the movie "The Blind Side."

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