The investigation into misconduct by the Justice Department lawyers who prosecuted the late Sen. Ted Stevens (R-Alaska) was recently made public. The investigators appointed by U.S. District Court Judge Emmet Sullivan concluded that the federal prosecutors involved in the case willfully and intentionally withheld exculpatory evidence from Stevens and his attorneys.

Even before the report’s release, Stevens’ former colleagues were pressing Attorney General Eric Holder to punish the individuals involved. This reaction is understandable, but it would be a shame if this episode does not remind Members of Congress that federal prosecutors, like all of us, are fallible. Their power should be limited and checked by the other branches to preserve individual liberty.

Look at our federal sentencing laws. Policymakers, the media and the public tend to judge the fairness of our sentencing laws vertically and horizontally; they want to know: 1) that the sentences being handed down are appropriate for the crime; and 2) that similar offenders who commit similar crimes are being treated, well, similarly. Yet, too often, they look only at the final stage of sentencing, when the federal judge announces the sentence. This myopia ignores all of the ways that prosecutors’ actions influence the outcome before that last step.

That prosecutors wield enormous power is not a new revelation. More than 70 years ago, then-Attorney General Robert Jackson, who would later serve on the Supreme Court and as a prosecutor at the Nuremberg Trials, told an assembly of U.S. attorneys that “the prosecutor has more control over life, liberty and reputation than any other person in America. His discretion is tremendous. He can have citizens investigated and, if he is that kind of person, he can have this done to the tune of public statements and veiled or unveiled intimations. … The prosecutor can order arrests, present cases to the grand jury in secret session and, on the basis of his one-sided presentation of the facts, can cause the citizen to be indicted and held for trial. He may dismiss the case before trial, in which case the defense never has a chance to be heard. Or he may go on with a public trial. If he obtains a conviction, the prosecutor can still make recommendations as to sentence, as to whether the prisoner should get probation or a suspended sentence.”

Jackson suffered no delusion about what the aggregation of power in one federal officeholder meant: “While the prosecutor at his best is one of the most beneficent forces in our society, when he acts from malice or other base motives, he is one of the worst.”

Jackson did not live to see the explosion in mandatory minimum sentencing laws and the creation of the federal sentencing guidelines, which, until the Supreme Court’s decision in United States v. Booker, were mandatory.

Mandatory sentencing laws have dramatically increased the power of prosecutors relative to the other actors in the criminal justice system. They have done so by eliminating the ability of judges to provide a check on prosecutorial authority at the sentencing stage. Thus, prosecutors are no longer limited to making recommendations as to sentence, as Jackson observed. Prosecutors now have the power to specify the ultimate sentence through their initial charging decision.

One does not have to have blind faith in judges to prefer a criminal justice system that protects their discretion. When judges make mistakes, as they will necessarily do, their judgments can be appealed and overturned. The same is not true of prosecutors. Their most important decisions are unreviewable by any court and almost always shielded from public scrutiny.

The concentration of power in one federal actor’s hands should concern everyone who believes, along with our founders, that liberty is most secure when power is divided and subject to checks and balances. For even when that awesome power — to investigate, to indict, to prosecute — is not abused, as it clearly was in the case of Stevens, it must be checked.

Because mandatory sentencing laws eliminate any check on prosecutorial power, Members of Congress should oppose them.

Julie Stewart is president of Families Against Mandatory Minimums.