A Chester County man admitted he cast an illegal ballot in his son’s name during the 2020 presidential election, and has been barred from voting again for four years, prosecutors said Monday.

Ralph Thurman, 72, entered a guilty plea to repeat voting in elections during a hearing Friday before Chester County Court Judge Jeffrey R. Sommer. As part of the negotiated plea, Thurman was sentenced to three years’ probation.

Thurman’s attorney, Jeffrey Oster, described the incident as a mistake made during a frenzied and unusual voting process.

“Mr. Thurman maintains his innocence and continues to contend that this entire incident stems from a miscommunication at the voting center where the poll workers were speaking to him in a loud gymnasium through masks and a thick plexiglass barrier,” Oster said. “Had this not been an exceptionally contentious election year in the middle of a global pandemic, none of this would have occurred.”

It was unclear for whom Thurman cast the two ballots.

Police in Willistown Township charged Thurman on Nov. 13, touting his case as a documented example of voter fraud in Pennsylvania. Thurman, a registered Republican, cast his own ballot without incident on Election Day, but asked a poll worker if he could also vote on behalf of his son, according to the affidavit of probable cause for his arrest.

The poll worker told Thurman that he could not, and the older man left without incident, the affidavit said. Less than an hour later, the same poll worker noticed a man who resembled Thurman wearing a hat and sunglasses. The voter signed the polling place’s log as “Kyle Thurman,” a registered Democrat, and the son of Ralph Thurman.

When the poll worker realized that the disguised Thurman had cast a second vote illegally, he notified the judge of elections, who attempted to speak with Thurman. But Thurman left the building before workers could stop him, according to the affidavit.

Four other Pennsylvania residents have been charged with similar crimes in connection with voting in the 2020 election. Marple Township resident Bruce Bartman pleaded guilty in April to casting an absentee ballot for Donald Trump on behalf of his dead mother. Robert Richard Lynn, of Luzerne County, entered a guilty plea to similar charges in August.

Two Bucks County women — Melissa Ann Fisher and Deborah Elaine Dooner — have pending criminal cases, also for casting ballots in the names of their recently deceased mothers.