Paula Duncan, one of the jurors who convicted former Trump campaign chairman Paul Manafort, in Washington on Friday. (Jim Bourg/Reuters)

ONE OF the jurors from the recently concluded trial of Paul Manafort has described herself as a strong supporter of President Trump. She said she drove every day to the Alexandria courthouse where Mr. Trump’s former campaign chairman was being tried with her “Make America Great Again” cap in the back seat, and that she planned to vote again for Mr. Trump if he runs for reelection in 2020. She said she thought prosecutors had targeted Mr. Manafort as a way to get dirt on Mr. Trump, and that she didn’t want Mr. Manafort to be guilty. Nonetheless, she voted to convict him because the evidence of his guilt “was overwhelming.”

The account by juror Paula Duncan is a reassuring testament to how justice works in the United States. It is one that Mr. Trump would do well to familiarize himself with before making any further claims about witch hunts, rigged systems and the allegedly unfair treatment of Mr. Manafort.

Ms. Duncan, during an interview with Fox News, provided the first and, so far, only insight into the jury deliberations that resulted in Mr. Manafort’s conviction Tuesday on five charges of tax fraud, two charges of bank fraud and one count of failure to disclose a foreign bank account. The jury couldn’t come to unanimous agreement on 10 other counts and a mistrial on those charges was declared. Ms. Duncan revealed that there was just one juror who held out on conviction on those counts, citing reasonable doubt. The other 11 jurors were convinced of Mr. Manafort’s guilt.

But what was most instructive — perhaps even inspiring — in Ms. Duncan’s retelling was the seriousness and diligence of the jury in undertaking its responsibilities. It never occurred to Ms. Duncan to try to get out of jury duty; she called it her duty as an American citizen. One juror drove more than 100 miles each day to the federal courthouse. By her account, the panel rigorously considered and applied the evidence. There were “even tears” during the four hard days of deliberations — but politics played no part whatsoever in the jury’s decision.

“I did not want Paul Manafort to be guilty,” she said, “but he was, and no one’s above the law.” That’s another concept the president would do well to familiarize himself with.