TEXARKANA, Texas (AP) – A federal judge in East Texas has declined to reduce the 18-year prison sentence imposed on a woman for sending ricin-laced letters to former President Barack Obama and others.

The Texarkana Gazette reports that 40-year-old Shannon Richardson had appealed her sentence on the grounds of ineffective counsel.

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Actress Shannon Rogers Guess Richardson August 7, 2011. Guess Richardson has been arrested in connection with the mailing of ricin-laced letters to President Barack Obama and New York City Mayor Michael Bloomberg. (Photo by Leslie Morris/Getty Images)

But Judge Caroline Craven in a ruling issued Wednesday determined her claims were without merit.

Members of US Secret Service Uniformed Division secure an area in front of White House in Washington, DC, on April 17, 2013 as a part of tightened security following the Boston marathon bomb blasts. A letter addressed to US President Barack Obama has preliminarily tested positive for the deadly poison ricin, the Federal Bureau of Investigation said on April 17. In a statement, the FBI said the investigation into the letter sent to Obama and another sent to Senator Roger Wicker was ongoing, adding there was “no indication of a connection” to the Boston Marathon bombings. (Photo credit: JEWEL SAMAD/AFP/Getty Images)

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Richardson, a former actress whose credits include the television series “The Walking Dead,” pleaded guilty in 2013 to a federal charge of possessing and producing a biological toxin.

Richardson was arrested earlier that year after authorities said she tried to implicate her estranged husband after he had filed for divorce.

Prosecutors said she mailed three letters outside Texarkana then went to police and claimed that her husband had done it.

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