The Texas actress who admitted making toxins to send to President Barack Obama and the mayor of New York was more intent on framing her husband than in killing prominent politicians, a federal prosecutor says.
Shannon Guess Richardson, 36, pleaded guilty in federal court in Texarkana on Tuesday (local time) to making the toxic agent ricin that was sent in letters in May to Obama, Mayor Michael Bloomberg and a gun control advocate.
"In a bizarre way, I don't know that Shannon ever wanted to hurt anyone except her husband. She set up an elaborate scheme to set up Mr Richardson," US Attorney Malcolm Bales said in an interview with Reuters.
Exposure to even a small amount of ricin can cause death and no known antidote exists.
As part of a deal reached with federal prosecutors, Richardson, 36, would spend 18 years in prison and then five years on supervised release in exchange for her guilty plea, according to court documents.
Richardson, whose career included minor television roles in shows such as The Walking Dead, tried to blame her husband for the letters, according to prosecutors.
Richardson told Shreveport, Louisiana police on May 30 that her husband, Nathan Richardson, was carrying out a plot to mail the toxin to Obama and Bloomberg.
"There is no evidence to indicate that anyone else is involved other than Shannon Richardson. But she's the one. You've seen movies like this ... a black widow sort of thing," Bales said.
In a court document signed by Richardson, she outlines how she extracted the toxin using castor beans, lye and syringes that she bought with her husband's credit card.
"We thought this was her Lifetime movie. It's really hard to tell a story like this in the same fashion over again. The story that she told about (her husband) really unraveled quickly. Thank God nobody was hurt," Bales said.
Ricin cases are relatively new and rare in the federal courts. Cases must be cleared by the a US counter-terrorism division before they are filed, Bales said.
Ricin, a highly toxic substance, is found naturally in castor beans, but it takes a deliberate act to manufacture it and use it to poison people, according to the US Centers for Disease Control and Prevention.