Brendan V. Sullivan Jr., a partner at the law firm of Williams & Connolly, was the senior trial counsel for Sen. Ted Stevens.

In late May, the Justice Department finally completed its three-year investigation of the miscreant prosecutors who obtained an illegal verdict against Sen. Ted Stevens in 2008. That verdict caused the Alaska Republican to lose his reelection bid and changed the balance of power in the Senate. The department’s actions in this matter have fallen too far short.

After the trial, new prosecutors — appointed after the original prosecutors were held in contempt for failing to produce documents — discovered that the government had engaged in wrongdoing affecting the case’s most important evidence. The conduct was so outrageous that newly appointed Attorney General Eric Holder concluded the case should immediately be dismissed. And when trial Judge Emmet Sullivan (no relation) dismissed the case in April 2009, he said it was the worst misconduct he had seen in 25 years on the bench.

Sullivan appointed an independent investigator, former federal prosecutor Henry Schuelke, who noted in a 500-page report that the prosecution was “permeated by the systematic concealment of significant exculpatory evidence which would have independently corroborated Senator Stevens’s defense and his testimony, and seriously damaged the testimony and credibility of the government’s key witnesses.”

The results of the Justice Department’s own investigation came in a 672-page report released in May. Its publication on the eve of Memorial Day weekend stood in sharp contrast to the many front-page stories the department’s public relations experts orchestrated during the unlawful prosecution of the senator.

Holder deserves credit for recognizing the extent of the prosecutors’ misconduct and seeking an immediate dismissal. The day after the case was dismissed, the attorney general went to the courthouse where Stevens was tried and personally swore in a new group of assistant U.S. attorneys. He told them: “Your job as assistant U.S. attorneys is not to convict people. Your job is not to win cases. Your job is to do justice. Your job is in every case, every decision that you make, to do the right thing.”

There could not be a clearer standard of conduct for our federal prosecutors.

Or so it seemed until the Justice Department’s report was released. Among its many conclusions:

l Some prosecutors engaged in “reckless professional misconduct.” This new term in the law appears to be an effort to characterize wrongdoing of a lesser grade than “intentional.”

l Prosecutors violated Justice’s obligations under constitutional principles (and department policy) by failing to disclose exculpatory statements by a chief witness and others. Specifically, the government failed to disclose that its chief witness obtained a false affidavit from a woman with whom he had sex when she was underage. This was of great significance to the defense, to show that the witness had suborned perjury on a prior occasion. Lies in a letter in which prosecutors purported to disclose information to which the defendant was entitled are characterized by the report as “poor judgment.” In any other situation, the department would call sending a false letter an “intentional” act.

l The government failed to disclose statements of its chief witness that contradicted written accounting records the government had introduced into evidence as accurate business records.

l One prosecutor engaged in “reckless professional misconduct” when he failed to correct the chief witness’s testimony at trial about when the witness first advised the government about a concocted story. It was crucial to the defense to learn when the witness made up the false testimony. The jury was entitled to know that the fabrication came only two weeks before trial. All prosecutors, not just one, knew that their chief witness concocted a story to deliver at trial — yet not one of them fulfilled his or her individual duty to correct the false testimony.

l Two prosecutors engaged in “reckless professional misconduct.” One received a 40-day suspension without pay; the other, a 15-day suspension without pay — “punishment” that pales next to the misconduct.

l One supervisor in the department’s Public Integrity Section was found to have “exercised poor judgment by failing to supervise certain aspects of the disclosure process.” There was no punishment at all for the most senior prosecutor in the case.

The department made no effort to attribute fault to the prosecutor who committed suicide during the course of the investigation. On balance, leaving him out of the report is a decent thing to do. But it is hard to square with the public’s right to know all of the elements of a case in which prosecutors, not the defendant, were the wrongdoers.

The underlying misconduct represents a shameful chapter in the Justice Department’s history. But the department’s failure to punish wrongdoers makes the scandal worse, and the failure makes a mockery of the attorney general’s effort to establish a standard of propriety that the goal of prosecutors is to do justice, not to win at all costs.

Consider the contrast between all this and the recent Secret Service scandal. Agents on the president’s detail received a quick, harsh punishment for their misconduct; some careers were ended. Yet prosecutors who obtained an illegal verdict by repeatedly violating the Constitution and introducing false evidence avoid meaningful punishment. The Justice Department advocates punishment for others in courtrooms across the country every day. You would think those tasked with upholding justice understand that real punishment is needed to maintain standards and deter wrongdoing.

The day Judge Sullivan dismissed the case, nullifying the illegal verdict against Stevens, the courtroom was packed. The former senator told the judge: “Your actions gave me new hope that others may be spared the similar miscarriages of justice.”

The department has said that such misconduct happens only rarely. But most times the defense does not find out when prosecutors hold back exculpatory evidence. The Innocence Project has shown in recent years that there is widespread injustice in our system and many wrongful convictions. It is hard to catch a wrongdoer prosecutor. When we do, the punishment must fit the crime. The Justice Department’s failure to adequately punish is unbecoming to the department and unfair to the thousands of honest prosecutors who do follow the law.

If we don’t learn from these mistakes, we are doomed to repeat this miscarriage of justice. And if this can happen to a U.S. senator in a Washington, D.C., courtroom, it can happen to anyone, anywhere in America.