John Thompson in 2007. Tony Deifell@wdydwyd

If you want to understand how Kyle Duncan, President Trump’s nominee to the United States Court of Appeals for the Fifth Circuit, would serve in that role, consider how he behaved toward my late husband, John Thompson.

J.T., as we called him, spent 18 years in prison, 14 of them on death row, for a murder he did not commit. When it emerged that prosecutors in the office of Harry Connick, who was the former New Orleans district attorney, had destroyed evidence of his innocence to gain that conviction, he was granted a new trial, at which he was acquitted.

After his release, J.T. considered the long list of innocent men sent to prison by prosecutors in that same office who had withheld evidence. It was clear to him, as it is to any impartial observer, that the district attorney’s office for New Orleans has a track record of failing to turn over favorable evidence to defendants.

In 2003, J.T. sued the prosecutors who had hidden the evidence in his case for failing to train their lawyers on the importance of turning over favorable evidence. The jury, considering the blatant destruction of evidence in J.T.’s case, awarded him $1 million for every year he was on death row — $14 million in total.

When the prosecutors appealed, they argued, with a straight face, that what had happened to J.T. was so outrageous and illegal that the New Orleans district attorney could not be held responsible. The case went all the way to the Supreme Court.

Enter Kyle Duncan, the man we are to believe has the fairness and temperament to be a federal judge.

Mr. Duncan is best known for his work in Washington, D.C., as the former general counsel for the Becket Fund for Religious Liberty, a conservative organization that “defends religious liberty for all.” He played a leading role in opposing the provision of the Affordable Care Act requiring employers to provide insurance coverage for contraceptives. Mr. Duncan also defended North Carolina’s photo ID law that the Court of Appeals for the Fourth Circuit wrote had targeted black voters “with almost surgical precision.” He also defended Louisiana’s ban on gay marriage in several different courts before the Supreme Court prohibited state bans on gay marriage.

While representing the prosecutors when the case went to the Supreme Court, Mr. Duncan was serving as what he later called “solicitor general” of Louisiana, a position that does not exist. He devised the argument that, although the district attorney had withheld evidence in many cases involving innocent men, there was no need to train lawyers in his office because they would have learned about their obligation in law school.

The Supreme Court sided with the prosecutors, 5 to 4. Mr. Duncan received the Louisiana District Attorneys Association award for outstanding service for his work on the case.

Kyle Duncan, the nominee for the 5th U.S. Circuit Court of Appeals, speaking at the Senate Judiciary Committee hearing in November. Bryn Stole/The Advocate

Mr. Duncan, I’m sure, represented his client — J.T. would always say that everyone deserves a lawyer. But the positions Mr. Duncan argued and won are not the positions of a man who can suddenly become a fair referee in the dozens of similar cases that would come before him as a judge. Mr. Duncan’s confirmation could serve as a declaration to prosecutors that winning at all costs remains, as it has been far too often in the past, the path to success.

As the Fifth Circuit hears cases from Louisiana, Mississippi and Texas, Mr. Duncan would be in a position to rule on the many appeals of cases that involve overly aggressive prosecutors, including the very same prosecutors he has so vehemently argued can, essentially, do nothing wrong.

There are real consequences of Mr. Duncan’s advocacy. Just after my husband was released from Louisiana’s infamous Angola prison, J.T. started Resurrection After Exoneration, an organization that provides a place for people to stay when they come home from prison. The organization also offers a safe space for young people to create art and for community programs that teach children how to use computers and formerly incarcerated people how to open small businesses, like a screen print shop and a barber shop.

J.T. had always told me that if he was finally able to get the money he won in court, he planned to expand Resurrection After Exoneration all over the country to help people returning home from prison.

My husband died this past October, much too soon. He was 55. No prosecutors were punished for their role in putting him in prison. Meanwhile, Mr. Duncan is being considered for a promotion.