Authorities say 31-year-old Fabian Lamar Britt entered the guilty plea Wednesday in U.S. District Court in Columbus.
Britt sent a 2011 letter to Obama while he was in Jack T. Rutledge state prison in Columbus, The Columbus Ledger-Enquirer reported. At the time, he was serving a 5-year sentence for a Cobb County burglary.
Assistant U.S. Attorney Crawford Seals outlined the contents of the letter for the court in the 25-minute hearing.
"I am going to kill you Obama," Seals said the letter stated. "My life means nothing and these voices that drive me are uncontrollable. I need to kill. I want someone to kill. That that someone is you. ... Be there soon."
In 2002, Britt was sentenced to 41 months in federal prison for threatening to kill then-President George W. Bush. That letter, too, was sent to the White House while Britt was incarcerated.
Britt's lawyer, Bill Mason, said his client is mentally ill.
"These are the rantings of a frustrated, mentally ill inmate," Mason said after the hearing. "He has a long documented psychiatric history. And it is a matter of public record. He did not have the ability to carry out any of the threats."
His sentencing is set for Jan. 30.
Information from: Columbus Ledger-Enquirer, http://ledger-enquirer.com
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