A Scotsman released from prison four years ago after spending two decades on Ohio's death row could be sent back to prison after he pleaded guilty Friday to threatening a judge who prosecuted his original case.

Ken Richey pleaded guilty to a felony retaliation charge and now faces up to three years in prison. He'll be sentenced May 7.

Richey agreed to plead guilty in exchange for prosecutors dropping a charge that he violated a protection order when he called the Putnam County courthouse in Ottawa this past New Year's Eve.

Investigators said Richey was at his home in Tupelo, Miss., when he left the threatening message for county judge Randall Basinger, warning that he was coming to get him.

Richey was on death row for 21 years after being convicted of setting a fire that killed a 2-year-old girl in 1986. He denied any involvement and became well-known in Britain, where there is no death penalty, as he fought for his release. Among his supporters were several members of the British Parliament and Pope John Paul II.

Following years of appeals, a federal court determined his lawyers mishandled the case, and his conviction was overturned. Putnam County prosecutors initially planned to retry him, but Richey was released in 2008 under a deal that required him to plead no contest to attempted involuntary manslaughter. He also was ordered to stay away from the northwest Ohio county and anyone involved in the case, including Basinger.

Richey, though, carried a lifetime of bitterness over his conviction, his friends said.

He returned to Scotland in 2008, and later came back to the U.S. where he was arrested in Minnesota in 2010 and charged with assaulting his 24-year-old son. Prosecutors have said Richey was still wanted on a warrant out of Minnesota.