Michael Morton was exonerated by DNA evidence this month after being wrongfully convicted of murdering his wife and serving nearly 25 years in prison in Texas. In seeking to prove Mr. Morton’s innocence, his lawyers found in recently unsealed court records evidence that the prosecutor in the original trial, Ken Anderson, had withheld critical evidence that may have helped Mr. Morton.

The judge reviewing the case allowed Mr. Morton’s lawyers, including those from the Innocence Project, which represents prisoners seeking exoneration through DNA evidence, to gather facts about the prosecutor’s conduct. The Innocence Project’s report makes a compelling case that Mr. Anderson, now a state judge, disobeyed “a direct order from the trial court to produce the exculpatory police reports from the lead investigator” in the case.

Mr. Morton’s lawyers have asked that the judge recommend a “court of inquiry” to investigate whether Mr. Anderson violated the law and should be charged in a criminal proceeding. While this process is an urgent matter for Mr. Morton, it is also a test of American justice — whether a prosecutor who flouts his duty under the Constitution to disclose crucial evidence to a defendant is subject to any meaningful sanction.

Prosecutors have enormous power in determining who is subjected to criminal punishment because they have broad discretion in deciding criminal charges. The Brady rule, established by the Supreme Court in 1963, is supposed to be an important check on that power. It requires prosecutors to disclose evidence favorable to the defendant. But their failure to comply is rarely discovered, and, even then, prosecutors are almost never punished.