Prosecutorial Misconduct as a Ground for Post-Conviction Relief

By Elizabeth Franklin-Best, Esq., and Christopher Zoukis, JD, MBA

What is prosecutorial misconduct, and when does it justify relief?

Prosecutorial misconduct is conduct by a government lawyer that violates a defendant’s constitutional rights. Under Donnelly v. DeChristoforo and Darden v. Wainwright, it justifies vacating a conviction only where it “so infected the trial with unfairness as to make the resulting conviction a denial of due process,” or where it violates a specific guarantee like the knowing use of false testimony.

Key takeaways on prosecutorial misconduct claims

• Improper is not the same as unconstitutional. Courts regularly find a prosecutor’s conduct improper and affirm the conviction anyway. Donnelly holds that “not every trial error or infirmity which might call for application of supervisory powers correspondingly constitutes a ‘failure to observe that fundamental fairness essential to the very concept of justice.'”
• The controlling test is fundamental fairness, judged in context. Darden asks whether the comments “so infected the trial with unfairness as to make the resulting conviction a denial of due process,” weighing invited response, curative instructions, and the weight of the evidence.
• Which standard applies depends on what the conduct violated. Where a specific Bill of Rights guarantee is implicated — the Fifth Amendment privilege in Griffin v. California — that guarantee governs, not the general due process test.
• Knowing use of false testimony is the exception that favors the movant. After Glossip v. Oklahoma (2025), once falsity and government knowledge are shown, the prosecution ordinarily must establish harmlessness beyond a reasonable doubt.
• Most misconduct claims belong on direct appeal. A claim not raised there faces the cause-and-actual-prejudice bar of United States v. Frady — “to obtain collateral relief a prisoner must clear a significantly higher hurdle than would exist on direct appeal.”
• The prosecutor’s dual role is the source of the doctrine. Berger v. United States: the government’s “interest, therefore, in a criminal prosecution is not that it shall win a case, but that justice shall be done.”

What is prosecutorial misconduct?

Prosecutorial misconduct is conduct by a government lawyer that crosses from advocacy into a violation of the defendant’s rights. The phrase covers a range of behavior — improper argument, vouching for a witness, misstating evidence, commenting on the defendant’s silence, presenting testimony the government knows is false, abusing the grand jury, breaching a plea agreement, and failing to disclose favorable evidence.

The classic statement of the boundary is Berger v. United States, 295 U.S. 78 (1935), which remains the most quoted passage in this area of law:

“The United States Attorney is the representative not of an ordinary party to a controversy, but of a sovereignty whose obligation to govern impartially is as compelling as its obligation to govern at all; and whose interest, therefore, in a criminal prosecution is not that it shall win a case, but that justice shall be done.”

And the operative line:

“He may prosecute with earnestness and vigor — indeed, he should do so. But, while he may strike hard blows, he is not at liberty to strike foul ones. It is as much his duty to refrain from improper methods calculated to produce a wrongful conviction as it is to use every legitimate means to bring about a just one.”

Berger also explains why misconduct is dangerous in a way that other trial errors are not: “the average jury, in a greater or less degree, has confidence that these obligations, which so plainly rest upon the prosecuting attorney, will be faithfully observed. Consequently, improper suggestions, insinuations and, especially, assertions of personal knowledge are apt to carry much weight against the accused when they should properly carry none.”

The conduct the Court found improper in Berger is worth naming, because it establishes the baseline: the prosecutor was “guilty of misstating the facts in his cross-examination of witnesses; of putting into the mouths of such witnesses things which they had not said; of suggesting by his questions that statements had been made to him personally out of court, in respect of which no proof was offered; … of bullying and arguing with witnesses; and in general, of conducting himself in a thoroughly indecorous and improper manner.” That was a pronounced and persistent pattern in a case the Court described as not strong on the evidence. Isolated remarks are a different problem with a different answer.

One category is deliberately not covered here. Suppression of favorable evidence is misconduct, but it has its own three-element framework and its own body of law — see our page on what a Brady violation is and how suppressed evidence is raised as a §2255 claim, and, for what the government is obligated to turn over in the first place, exculpatory evidence and Brady lists.

Does misconduct automatically overturn a conviction?

No — and this is the single most important thing to understand before evaluating a claim. A court can find that a prosecutor behaved improperly, say so in a published opinion, and affirm the conviction in the same paragraph. That is the ordinary outcome, not an anomaly.

The governing test comes from Donnelly v. DeChristoforo, 416 U.S. 637 (1974). Where the claim is not that a specific constitutional guarantee was denied, the question is whether the conduct “so infected the trial with unfairness as to make the resulting conviction a denial of due process.” Donnelly drew the line expressly: “not every trial error or infirmity which might call for application of supervisory powers correspondingly constitutes a ‘failure to observe that fundamental fairness essential to the very concept of justice.'” It warned against reading ambiguity uncharitably — “a court should not lightly infer that a prosecutor intends an ambiguous remark to have its most damaging meaning or that a jury, sitting through lengthy exhortation, will draw that meaning from the plethora of less damaging interpretations.” And it insisted on preserving “the distinction between ordinary trial error of a prosecutor and that sort of egregious misconduct” that denies due process.

Darden v. Wainwright, 477 U.S. 168 (1986), applied that test and is the case that shows how demanding it is. The Court assumed the prosecutor’s closing argument was improper — it was, by any measure — and still found no due process violation, weighing four things:

1. Invited response. “Much of the objectionable content was invited by or was responsive to the opening summation of the defense.” As Young explains, this is “used not to excuse improper comments, but to determine their effect on the trial as a whole.”
2. Curative instructions. “The trial court instructed the jurors several times that their decision was to be made on the basis of the evidence alone, and that the arguments of counsel were not evidence.”
3. The weight of the evidence. “[O]verwhelming eyewitness and circumstantial evidence to support a finding of guilt on all charges … reduced the likelihood that the jury’s decision was influenced by argument.”
4. Whether the remarks manipulated or misstated the evidence as opposed to being intemperate.

United States v. Young, 470 U.S. 1 (1985), states the same principle for federal trials: “a criminal conviction is not to be lightly overturned on the basis of a prosecutor’s comments standing alone, for the statements or conduct must be viewed in context; only by so doing can it be determined whether the prosecutor’s conduct affected the fairness of the trial.”

A note on which court’s standard applies to you. Donnelly and Darden are federal habeas review of state convictions, and both stress that the standard there is “the narrow one of due process, and not the broad exercise of supervisory power.” Young is a federal prosecution, and it is the case that governs what a federal court may do about a federal prosecutor — including the exercise of supervisory power that Donnelly and Darden held unavailable on state habeas review. If your conviction is federal, Young is the closer analogue on direct appeal; the due process floor from Donnelly and Darden is what survives to collateral review.

The categories of prosecutorial misconduct, and what each requires

Misconduct claims are not analyzed under a single test. Which standard applies depends on what the conduct actually violated — a point Donnelly made explicitly by distinguishing cases “in which the State has denied a defendant the benefit of a specific provision of the Bill of Rights” from cases where the claim is only that a remark rendered the trial unfair.

Table 1. Categories of prosecutorial misconduct — the constitutional provision implicated, the controlling authority, and the showing required to obtain relief.

Conduct	Constitutional provision implicated	Controlling authority	What the movant must show
Knowing use of false testimony, or failure to correct it	Due Process (5th/14th Am.)	Napue v. Illinois, 360 U.S. 264 (1959); Glossip v. Oklahoma, 604 U.S. 226 (2025)	The witness testified falsely and the government knew it. Materiality is then favorable: relief follows if the false testimony “could in any reasonable likelihood have affected the jury’s judgment” — ordinarily requiring the government to establish harmlessness beyond a reasonable doubt
Comment on the defendant’s failure to testify	Fifth Amendment privilege against self-incrimination	Griffin v. California, 380 U.S. 609 (1965)	That the prosecutor commented on the accused’s silence, or the court instructed that silence is evidence of guilt. Griffin holds the Fifth Amendment “forbids either”
Improper vouching; expressing personal belief in guilt or witness credibility	Due Process / right to be tried on the evidence	Berger v. United States, 295 U.S. 78 (1935); United States v. Young, 470 U.S. 1 (1985)	That the remarks conveyed that undisclosed evidence supports the charge, or lent “the imprimatur of the Government” to the witness — and, in context, affected the fairness of the trial
Misstating evidence; arguing facts not in evidence; bullying witnesses	Due Process	Berger, 295 U.S. 78; Donnelly v. DeChristoforo, 416 U.S. 637 (1974)	Conduct “pronounced and persistent,” not isolated, that “so infected the trial with unfairness as to make the resulting conviction a denial of due process”
Breach of a plea agreement	Due Process	Santobello v. New York, 404 U.S. 257 (1971)	That the plea rested “in any significant degree on a promise or agreement of the prosecutor” that was not fulfilled. Prejudice is not required — an inadvertent breach still requires a remedy
Grand jury abuse (nonconstitutional error)	Fifth Amendment grand jury clause; Fed. R. Crim. P. 6 and 52(a)	Bank of Nova Scotia v. United States, 487 U.S. 250 (1988)	That the violation “substantially influenced the grand jury’s decision to indict,” or that there is “grave doubt” the decision was free from that influence. Structural compromises are presumed prejudicial
Suppression of favorable evidence	Due Process	Brady v. Maryland, 373 U.S. 83 (1963) — covered on its own page	Favorable + suppressed + material. See Brady violation

Read across that table and the practical point is unmistakable: the burden of proof is not the same in every row. A claim framed as generic “improper argument” carries the heaviest burden on the movant. The same facts framed as knowing use of false testimony shift the burden to the government. Framing is not cosmetic here.

Applied Insight — Elizabeth Franklin-Best, Esq., Principal Attorney: The first question we ask about a misconduct allegation is not “was this improper” — it usually was — but “which constitutional provision does it actually implicate.” That determines the test, the burden, and often whether the claim survives at all. A prosecutor who told the jury he personally believed a cooperating witness is one thing under the general due-process standard. If the record also shows the government knew what that witness said was untrue, it is a different claim with a different burden allocation. Reading the transcript for what was said is the easy half. Reading it for which guarantee was breached is the half that decides the motion.

What is improper vouching?

Improper vouching is a prosecutor’s assurance of a witness’s credibility, or a statement of personal belief in the defendant’s guilt, that rests on something other than the evidence the jury heard.

United States v. Young, 470 U.S. 1 (1985), identifies the two distinct harms:

“such comments can convey the impression that evidence not presented to the jury, but known to the prosecutor, supports the charges against the defendant and can thus jeopardize the defendant’s right to be tried solely on the basis of the evidence presented to the jury; and the prosecutor’s opinion carries with it the imprimatur of the Government and may induce the jury to trust the Government’s judgment rather than its own view of the evidence.”

Young also quotes the ABA standard the Court found “useful”: “[i]t is unprofessional conduct for the prosecutor to express his or her personal belief or opinion as to the truth or falsity of any testimony or evidence or the guilt of the defendant.”

That is the rule. Three qualifications determine whether a vouching claim goes anywhere.

Arguing credibility from the evidence is not vouching. A prosecutor may tell the jury a witness was consistent, corroborated, and had no motive to lie, so long as the argument is anchored in what the jury heard. The line is between inference from the record and assurance from the government’s own credibility.

Invited response matters, but it is not a license. Young held that “if the prosecutor’s remarks were ‘invited,’ and did no more than respond substantially in order to ‘right the scale,’ such comments would not warrant reversing a conviction” — while cautioning that courts do not intend “to encourage prosecutors to respond to the ‘invitation.'” The proper course when defense counsel goes out of bounds is to object and ask for a curative instruction.

Where there was no objection, the standard hardens. On direct appeal, unobjected error is reviewed for plain error under Fed. R. Crim. P. 52(b), which Young describes as reaching only “particularly egregious errors” — those that “seriously affect the fairness, integrity or public reputation of judicial proceedings” — and as an exception to be “used sparingly, solely in those circumstances in which a miscarriage of justice would otherwise result.” On collateral review the standard is harder still, as set out below.

There is a second path worth knowing about. Where trial counsel sat silent through vouching that a competent lawyer would have objected to, the theory may be ineffective assistance of counsel — measured against the two-prong test explained on our page on what Strickland requires — rather than misconduct — which converts the claim into one that belongs on collateral review by design and supplies its own answer to procedural default.

What if the prosecutor knew a witness lied?

This is the strongest misconduct claim in federal practice, and after 2025 it is stronger than it was.

Napue v. Illinois, 360 U.S. 264 (1959), holds that “a conviction obtained through use of false evidence, known to be such by representatives of the State, must fall under the Fourteenth Amendment.” Two features of Napue expand it well beyond outright perjury solicited by the government:

• The government need not have solicited the falsehood. The same result obtains where the State allows known false testimony to stand uncorrected.
• Falsity about credibility alone is enough. The rule “does not cease to apply merely because the false testimony goes only to the credibility of the witness.” A cooperator who falsely denies having a deal has given false testimony within Napue even if everything he said about the offense was true.

Glossip v. Oklahoma, 604 U.S. 226 (2025), applied Napue to reverse a capital conviction and restated the standard in terms that matter enormously for anyone evaluating a claim:

“If a violation is established, a new trial is warranted if the false testimony could in any reasonable likelihood have affected the jury’s judgment; meaning, ordinarily, that the prosecution must establish harmlessness beyond a reasonable doubt.”

Glossip added two clarifications. First, “the Due Process Clause imposes the duty to correct false testimony on the State, not the defense” — a prosecutor cannot answer a Napue claim by arguing the defense should have caught it. Second, Napue “does not require that the false testimony itself must have directly affected the trial’s outcome”; the question is whether the failure to correct could have contributed to the verdict.

Compare that with the general misconduct standard, where the movant must show the conduct so infected the trial as to deny due process, and with Brady, where the movant must show a reasonable probability of a different result. Under Napue, once falsity and knowledge are established, the burden effectively moves to the government.

Two limits keep this from being available in every case. Actual falsity must be shown — testimony the defense merely disputes is not false testimony. And at least one circuit has held that where the defense itself elicits the alleged perjury on cross-examination, no Napue violation occurs because the government did not knowingly present it. That rule is not uniform, and it is worth checking how your circuit treats it before building a motion on cross-examination testimony.

What if the government broke my plea agreement?

A broken promise in a plea agreement is its own violation, and it is the one category on this page where the movant does not have to prove that the breach changed the outcome.

Santobello v. New York, 404 U.S. 257 (1971), states the rule: “when a plea rests in any significant degree on a promise or agreement of the prosecutor, so that it can be said to be part of the inducement or consideration, such promise must be fulfilled.” Three features of Santobello are worth knowing precisely, because they are frequently misdescribed:

Inadvertence is no defense. The prosecutor who breached in Santobello was a successor who did not know about the promise. The Court’s response: “The staff lawyers in a prosecutor’s office have the burden of ‘letting the left hand know what the right hand is doing’ or has done. That the breach of agreement was inadvertent does not lessen its impact.”

No showing of actual influence is required. The sentencing judge stated the recommendation had not influenced him, and the Court accepted that — and still remanded. “We need not reach the question whether the sentencing judge would or would not have been influenced had he known all the details of the negotiations for the plea.” That is a materially lighter burden than any other category here.

The remedy is not automatic withdrawal of the plea. Santobello left the choice to the court on remand: “specific performance of the agreement on the plea, in which case petitioner should be resentenced by a different judge, or … the opportunity to withdraw his plea of guilty.” Specific performance — resentencing before a different judge with the government keeping its promise — is a common outcome.

What counts as a breach is a question of construing the agreement, and it is not limited to a broken sentencing recommendation. Making the agreed recommendation in a tone that undercuts it, arguing facts that contradict a stipulation, or advocating for a guideline enhancement the government agreed not to seek have all been litigated as breaches. The reverse question — whether your own waiver of the right to appeal or to file a §2255 motion is enforceable against you — is a separate subject covered on our page on appeal and collateral-attack waivers.

Grand jury abuse and misconduct before indictment

Misconduct in the grand jury is real, and the remedy is narrow. Bank of Nova Scotia v. United States, 487 U.S. 250 (1988), holds that “as a general matter, a district court may not dismiss an indictment for errors in grand jury proceedings unless such errors prejudiced the defendants,” and that “a federal court may not invoke supervisory power to circumvent the harmless-error inquiry prescribed by Federal Rule of Criminal Procedure 52(a).”

The prejudice standard is specific: dismissal is appropriate “only ‘if it is established that the violation substantially influenced the grand jury’s decision to indict,’ or if there is ‘grave doubt’ that the decision to indict was free from the substantial influence of such violations.”

There is an exception for structural defects. Where “the structural protections of the grand jury have been so compromised as to render the proceedings fundamentally unfair,” prejudice is presumed — the Court’s examples being racial discrimination in grand juror selection and the exclusion of women from the grand jury.

Bank of Nova Scotia also names the alternatives courts use instead of dismissal, which is useful context for anyone deciding what to ask for: “a knowing violation of Rule 6 may be punished as a contempt of court. In addition, the court may direct a prosecutor to show cause why he should not be disciplined and request the bar or the Department of Justice to initiate disciplinary proceedings against him. The court may also chastise the prosecutor in a published opinion.” The Court’s stated rationale — that these remedies “allow the court to focus on the culpable individual rather than granting a windfall to the unprejudiced defendant” — is the clearest available statement of why misconduct findings so often produce criticism rather than relief.

There is a further timing problem that ends most post-conviction grand jury claims before the standard is even reached: a petit jury’s guilty verdict generally renders harmless any nonconstitutional grand jury error, because the higher standard of proof has been met on the same charge. A grand jury claim that was not raised before trial is very difficult to resurrect on collateral review.

Can I raise prosecutorial misconduct in a 2255 motion?

Yes — 28 U.S.C. §2255(a) reaches a sentence “imposed in violation of the Constitution or laws of the United States,” and a due process violation qualifies. But most misconduct claims are visible in the trial record, which means they were available on direct appeal, which means they are procedurally defaulted if they were not raised there.

The governing case is United States v. Frady, 456 U.S. 152 (1982). Frady holds that the plain-error standard of Rule 52(b) “is out of place when a prisoner launches a collateral attack against a criminal conviction after society’s legitimate interest in the finality of the judgment has been perfected,” and reaffirms “the well-settled principle that to obtain collateral relief a prisoner must clear a significantly higher hurdle than would exist on direct appeal.” The applicable standard is cause and actual prejudice, and the prejudice showing is demanding: a movant “must shoulder the burden of showing, not merely that the errors at his trial created a possibility of prejudice, but that they worked to his actual and substantial disadvantage, infecting his entire trial with error of constitutional dimensions.”

That leaves four realistic routes for a misconduct claim on collateral review:

1. The claim was raised on direct appeal and rejected, and there is a genuinely new basis for revisiting it. This is narrow — relitigating a decided claim is generally not permitted.
2. Cause and prejudice. The most common cause is that the factual basis was not reasonably available — which is why the strongest collateral misconduct claims are Napue claims and suppression claims, where the government’s own concealment is the reason nobody raised it earlier. The doctrine, including what counts as cause, is set out on our page on procedural default and what excuses it.
3. Reframe it as ineffective assistance. Where counsel failed to object to misconduct that a reasonable lawyer would have challenged, the claim becomes an ineffective assistance of counsel claim — which the Supreme Court has held may be brought under §2255 whether or not it could have been raised on direct appeal.
4. Actual innocence as a gateway past the bar, which is a separate and demanding showing.

Where the claim survives to a merits ruling, the factual disputes it raises may require a 2255 evidentiary hearing — and if the claim rests on facts the record does not contain, the one-year clock may run from a later date than you assume, which is worked through on our §2255 deadline calculator.

Two vehicle points. A compassionate-release motion is not a substitute: Fernandez v. United States, 608 U.S. 411, 146 S. Ct. 1292 (2026), holds that a prisoner attacking the validity of a conviction must proceed under §2255 rather than §3582, and the §2255 one-year clock does not pause while a §3582 motion is pending — the trap addressed on our page on what to do after a compassionate-release denial that attacked your conviction. And whether a given claim belonged on direct appeal or on collateral review in the first place is covered on our page on choosing between a direct appeal and a §2255 motion.

If the district court denies relief, appealing requires a certificate of appealability under §2253(c). What happens between filing and ruling — screening, the government’s answer, discovery, a possible hearing — is set out on our page on what happens after filing a 2255.

Applied Insight — Christopher Zoukis, JD, MBA, Managing Director: The transcript is where this claim lives or dies, and it is the document families most often do not have. If a prosecutor’s closing argument is the problem, someone has to read the closing argument — and then read the defense closing that preceded it, because invited response is the government’s first answer, and read the jury instructions, because a curative instruction is the second. Ordering the trial transcript takes time and it is the single most useful thing to start early. The legal evaluation and any filing are handled by the firm’s attorneys.

How misconduct claims combine with Brady and ineffective-assistance claims

In practice these three theories arrive together, because a single course of conduct usually supports more than one of them. Keeping them analytically separate is what makes a motion coherent — and, under Rule 2(b) of the Rules Governing Section 2255 Proceedings, a movant must specify all available grounds and the facts supporting each.

The clean way to divide them is by asking whose conduct is the problem:

• The government failed to turn something over → Brady. Three elements: favorable, suppressed, material.
• The government affirmatively used or tolerated something false → Napue. Falsity plus knowledge, with the burden then largely on the government.
• The government behaved improperly in front of the jury → the Donnelly/Darden due process standard, or the specific guarantee implicated.
• Your own lawyer failed to object, investigate, or preserve → ineffective assistance of counsel.

The interaction that matters most is between the first two and the fourth. Suppression and false-testimony claims usually supply their own cause for a procedural default, because the government’s conduct is why nobody raised the claim earlier. Pure improper-argument claims do not — the argument happened in open court and counsel could have objected. That asymmetry is why the same set of facts can produce one claim the court reaches and another it refuses to hear.

Where a misconduct finding is part of a broader claim that the conviction is factually wrong, the full range of options — new evidence, innocence, and the realistic path through federal court — is set out on our page for someone wrongly convicted in federal court. And the broader inventory of what can and cannot be raised is on our pages on grounds for a §2255 motion and claims a court will refuse to hear.

Why work with Elizabeth Franklin-Best, P.C.

Elizabeth Franklin-Best, P.C. is a boutique federal criminal defense and appellate firm founded in 2019, running a national federal practice on an intentionally small caseload — federal criminal appeals, §2255 motions, §2241 petitions, sentence reductions, compassionate release, and clemency — with offices in Columbia and Mount Pleasant, South Carolina, and clients nationwide.

Elizabeth Franklin-Best is admitted to the U.S. Supreme Court and twelve of the thirteen U.S. Courts of Appeals — every regional circuit (1st–11th) plus the D.C. Circuit — and has been admitted pro hac vice in federal courts from Montana to Florida. Over more than 20 years she has handled more than 330 federal proceedings, over 100 of them appeals, with sixteen published decisions as counsel of record. She is recognized by Best Lawyers in America 2026 for Appellate Practice and by Chambers USA 2026 for white-collar litigation, was named South Carolina Public Defender of the Year in 2010, and is the author of Reversing Your Criminal Conviction: Develop Your Winning Strategy (2023).

Christopher Zoukis, JD, MBA, the firm’s Managing Director, leads its federal prison consulting work — Bureau of Prisons designation, sentence computation, First Step Act time credits, RDAP, and reentry planning. He is the author of the Federal Prison Handbook, Directory of Federal Prisons, Prison Education Guide, and College for Convicts, and serves as Chairman of the Board of the Human Rights Defense Center. He earned his J.D. at UC Davis School of Law after serving roughly a decade in the federal Bureau of Prisons, where he became an award-winning incarcerated journalist. Legal strategy and all filings are handled by the firm’s attorneys.

Misconduct claims are won on the record, not on the characterization. Evaluating one means reading the transcript against the standard that actually governs the conduct in question — which is the same close-reading work described on our page on what a federal 2255 motion lawyer does at each stage of a collateral proceeding.

Talk to a federal post-conviction lawyer

If you believe a federal prosecutor crossed a constitutional line in your case — at trial, before the grand jury, or in breaking a plea agreement — you can request a consultation for federal post-conviction review directly.

Schedule a consultation · Phone: (843) 620-1100 · Offices: Columbia and Mount Pleasant, South Carolina — serving clients in federal courts nationwide.

Bring the judgment, the docket sheet, the plea agreement if there was one, and the date the appeal concluded. If the claim concerns something said at trial, the transcript is the document that decides it, and it is worth ordering before the first conversation.

Frequently Asked Questions About Prosecutorial Misconduct

Reviewed for legal accuracy by Elizabeth Franklin-Best, Esq., Principal Attorney·September 2026