James McVay has been sentenced to death for a 2011 killing he said was part of a plot to assassinate President Barack Obama.

James McVay has been sentenced to death for a 2011 killing he said was part of a plot to assassinate President Barack Obama. Photo: AP

Sioux Falls, South Dakota: A judge has sentenced a man to death for killing a woman as part of what he said was a plot to assassinate US President Barack Obama.

The hearing on Tuesday formalised the unanimous vote of a jury to sentence 44-year-old James McVay to death. McVay would have been sentenced to life in prison without parole if the jury's decision had not been unanimous.

McVay pleaded guilty, but mentally ill, to murder in the 2011 stabbing of 75-year-old Maybelle Schein. McVay said he killed Schein and stole her car as part of his plan to drive to Washington and kill the president. He was later arrested in Madison, Wisconsin.

Schein's family declined to speak during the hearing. Prosecutors, McVay and his defence team also did not comment.

"I don't have a lot to say here," said Circuit Judge Peter Lieberman. "This is a situation where a jury's verdict has a lot more weight than what I could say."

Public defender Traci Smith filed a motion hours before the hearing asking Judge Lieberman to vacate the sentence based on remarks made by the prosecution during closing arguments last month.

Ms Smith argued that closing arguments about protecting the community "inflamed the passions" of the jury, creating a bias against McVay, the Argus Leader newspaper reported. Judge Lieberman rejected the motion, saying the jury reached a decision after a thoughtful process.

McVay's sentence will be automatically reviewed by the South Dakota Supreme Court.

AP