Exculpatory and Mitigating Evidence

Rule 3.8(a) tells a prosecutor what to refrain from doing: prosecuting a charge the prosecutor knows is not supported by probable cause.¹ Paragraph (d) tells the prosecutor what to do. It requires “timely disclosure to the defense of all evidence or information known to the prosecutor that tends to negate the guilt of the accused or mitigates the offense.”² At sentencing it adds a second command: the prosecutor must disclose to the defense and to the tribunal all unprivileged mitigating information the prosecutor knows, unless a protective order of the tribunal relieves the prosecutor of that responsibility.³

The duty follows from the prosecutor’s dual function, which entails duties not only to the public but also to the accused.⁴ It also follows from a fact about who holds the information: the prosecution alone can know what has not been disclosed.⁵ A defense lawyer cannot ask for a witness statement or laboratory result whose existence the lawyer does not know about, so the rule assigns disclosure to the only lawyer who can see the file. That assignment is how the minister-of-justice ideal works in practice. The prosecutor represents a sovereign whose interest, as Berger put it, is “not that it shall win a case, but that justice shall be done.”⁶

Four points organize the rest of this section. The first is what the core duty requires and what triggers it. The second is how far the duty reaches, which depends on what the prosecutor knows. The third is what the sentencing clause and the protective-order exception add. The fourth is how the ethics rule differs from the separate constitutional duty that takes its name from Brady v. Maryland, which has a different source and is enforced through a different remedy.

Duty to Disclose Favorable Evidence

Each phrase in the first clause of paragraph (d) does separate work. “Tends to negate” asks only whether the item points away from guilt; it need not prove innocence or settle the case. “Mitigates the offense” covers information that reduces the offense’s seriousness or the punishment it deserves. “Evidence or information” reaches a witness’s oral remark as readily as a laboratory report. And “timely” ties the duty to usefulness, because disclosure that arrives after the defense has committed to a theory, or after the verdict, gives the defense little to work with.

The duty is affirmative, and that separates it from the rules every lawyer already follows. Under Model Rule 3.4, a lawyer may not unlawfully obstruct another party’s access to evidence or conceal material with potential evidentiary value, and must make a reasonably diligent effort to comply with a proper discovery request. Those rules respond to something the lawyer does or something the opponent asks for. The typical advocate need not volunteer evidence that may hurt the client’s case. Paragraph (d) makes the prosecutor volunteer evidence that hurts the government’s case, and its text conditions disclosure on no request from the defense.⁷

The text also omits something. The prosecutor’s constitutional duty reaches only evidence material to guilt or punishment, while Rule 3.8(d) does not expressly include a materiality requirement.⁸ The rule’s trigger is whether the item tends to negate guilt or mitigate the offense, and it never asks the further question whether the item would change the result. The ethics standard stresses the point: the duty applies “regardless of whether the prosecutor believes it is likely to change the result of the proceeding.”⁹ The rule is best read as telling the prudent prosecutor to avoid even the temptation of a self-serving judgment about whether favorable evidence is important enough to disclose.¹⁰

Two reasons explain why the rule takes that judgment out of the prosecutor’s hands. The first is that no one can reliably predict an item’s significance early. United States v. Agurs observed, in discussing the constitutional duty, that the standard is inevitably imprecise and that the significance of an item “can seldom be predicted accurately until the entire record is complete,” so “the prudent prosecutor will resolve doubtful questions in favor of disclosure.”¹¹ A laboratory note that looks harmless beside the government’s theory may become the missing piece once the defense connects it to a witness or an alibi the prosecutor has never heard of.

The second reason is incentive. The prosecutor deciding what to disclose has already concluded that the defendant is guilty beyond a reasonable doubt, because that conclusion produced the charges, so conscientious prosecutors must constantly train themselves to view the evidence contrary to the conclusion they have already drawn.¹² A rule that let that same lawyer decide whether favorable evidence matters would ask the person with the most to gain from a “no” to give the answer.

Kyles v. Whitley approved of disclosure in doubtful cases: “This is as it should be.” Such disclosure justifies trust in the prosecutor as the sovereign’s representative and tends to preserve the criminal trial, rather than the prosecutor’s private deliberations, as the forum for ascertaining the truth, so “[t]he prudence of the careful prosecutor should not therefore be discouraged.”¹³ Uncertainty about where the line falls does not excuse silence either. The Court noted in Connick v. Thompson that prosecutors are ethically bound to know what Brady entails and to perform legal research when they are uncertain.¹⁴ A prosecutor in doubt therefore has two honest options, which are to research the question or to disclose, and withholding on a private guess is not among them.

The Duke lacrosse prosecution shows what the rule guards against. North Carolina District Attorney Michael Nifong failed to disclose to the defendants that laboratory tests indicated the DNA found on the complaining witness did not come from them, and the outrage that followed led to his disbarment.¹⁵ A DNA result that excludes the accused tends to negate guilt on any reading, so paragraph (d) required timely disclosure and left no judgment about weight to exercise. The principle behind criminal discovery generally is that trial by ambush is unfair, and there is much more at stake in a criminal trial than in a sporting event.¹⁶

Hypothetical Illustration

A prosecutor handling a burglary case holds two items. One is a laboratory report confirming that the defendant’s fingerprints were on the window frame. The other is a note of a phone call from a neighbor, who says he saw a man he knows by name leaving the house that night and that the man was not the defendant. The prosecutor believes the neighbor has the date wrong and that no jury would credit the call. The fingerprint report only confirms the government’s theory, so it is not information that tends to negate guilt or mitigates the offense, and paragraph (d) does not require it to be handed over as favorable evidence, though whether some other discovery rule reaches it is a separate question. The neighbor’s call points toward a different offender and so tends to negate guilt. The prosecutor’s low opinion of its reliability is exactly the judgment the rule removes, and timely disclosure is required so the defense can decide what to do with it.

The dividing line in that file separates items that point away from guilt or toward a lesser offense from items that merely confirm the government’s case. The prosecutor’s estimate of how persuasive the favorable item will be sits on neither side of the line, which is why it cannot justify withholding.

Known to the Prosecutor

Paragraph (d) reaches “evidence or information known to the prosecutor,” and those words mark the outer limit of the ethics duty.¹⁸ The prosecutor must actually know of an item before failing to disclose it can violate the rule. Discipline attaches to conduct a lawyer can control, and investigative files in a serious case are large, assembled by many people, and sometimes disorganized, so a rule that punished every missed item would demand perfection. Rule 3.8(d) is neither a trap for the unwary nor a prescription for perfection: a prosecutor should not be disciplined because an extraneous, arguably exculpatory or mitigating item is later found in a government file when the prosecutor had not found it and had not recognized it, at the time, as falling within the disclosure duty.¹⁹

That protection covers honest oversight and stops short of willful ignorance. The rule does not forgive willful ignorance about the information contained in the records and evidence the government has gathered.²⁰ The prosecutor chooses what to read, so if chosen ignorance defeated the knowledge element, the easiest way to avoid the duty would be never to look. An exam stem about a favorable note that surfaces after the verdict therefore turns on how the note stayed unseen.

A clean ethics position under paragraph (d) does not end the analysis, because the constitutional duty reaches further. In Kyles v. Whitley, a decision applying the Brady due process rule and not interpreting Rule 3.8(d), the Court held that the prosecution, which alone can know what is undisclosed, must gauge the likely net effect of all the favorable evidence and make disclosure when the point of “reasonable probability” is reached. It follows, the Court said, that the individual prosecutor has a duty to learn of any favorable evidence known to the others acting on the government’s behalf in the case, including the police.²¹ Good faith does not change the result: whether a failure to disclose is in good faith or bad faith, the prosecution’s responsibility for failing to disclose known, favorable evidence rising to a material level of importance is inescapable.²²

The two duties therefore ask different questions about the same file. The ethics rule asks what the prosecutor personally knew, because discipline falls on an individual lawyer and has to track that lawyer’s own state of mind. The constitutional rule protects the fairness of the trial, and its remedy corrects the verdict, so it can charge the government with what its agents knew. The prosecutor who never opened the binder may thus escape discipline and still face a constitutional claim, whose materiality requirement is taken up at the end of this section.

Giglio v. United States resolved the same problem inside a single office. The government’s key witness, Taliento, denied on cross-examination that he had been promised leniency, but a prosecutor at an earlier stage had told him he would not be prosecuted if he testified, and the trial prosecutor never told the defense.²³ The Court treated the prosecutor’s office as an entity and the spokesman for the government, so a promise by one attorney was attributed to the government, and it ordered a new trial.²⁴ The trial prosecutor’s personal ignorance did not matter, because the witness’s credibility was central to the case and the jury was entitled to know of any understanding about his future prosecution.

Giglio also answered the objection that attribution burdens large offices: the Court observed that procedures and regulations can be established to carry that burden and to insure communication of all relevant information on each case to every lawyer who deals with it.²⁵ An office might, for example, require investigators to forward everything they collect and require that any promise made to a witness be recorded where the trial lawyer will see it. Such procedures close the gap between what the office knows and what the trial prosecutor knows. A prosecutor who bypasses them to stay uninformed is practicing the willful ignorance the ethics rule does not forgive.

Sentencing and Protective Orders

Paragraph (d) closes with two features that complete the duty. After requiring timely disclosure of evidence that tends to negate guilt or mitigates the offense, the text adds that “in connection with sentencing” the prosecutor must “disclose to the defense and to the tribunal all unprivileged mitigating information known to the prosecutor, except when the prosecutor is relieved of this responsibility by a protective order of the tribunal.”²⁷ Two things set that clause apart from the general duty. The audience now includes the tribunal, the court that will impose the sentence, along with the defense. And the subject is limited to mitigating information that is unprivileged. Mitigating information lowers the seriousness of the offense or the punishment it deserves, and it can do so without negating guilt, so the clause does most of its work after a guilty plea or a verdict, when only the sentence remains open.

The reason to send the information to the tribunal as well as to the defense follows from who decides the sentence. The judge weighs the mitigating facts, such as the defendant’s role in the offense. Information that reached only the defense would depend on defense counsel to put it before the judge, while information that also reaches the judge is in front of the decision maker. The prosecutor holds the file, so the rule burdens the prosecutor with passing it on. “Unprivileged” keeps protected communications outside the clause.

The only exception is a protective order, a court’s ruling that relieves a party of an obligation that would otherwise apply. Rule 3.8(d) allows a prosecutor to withhold exculpatory or mitigating evidence “when the prosecutor is relieved of this responsibility [of disclosure] by a protective order of the tribunal.” If disclosure would harm an individual or the public interest, as with information about confidential informants, the prosecutor may ask the court for authority to withhold or redact the information. The court then decides whether the accused’s need for the information to ensure a fair trial or a fair sentence overrides the purpose of protecting a person or interest from harm.²⁸

The rule routes the informant-safety concern to a judge for the same reason it removed the materiality judgment from the prosecutor. A prosecutor who decided privately that disclosure was too dangerous would be deciding a question in which the prosecutor has a stake, while a neutral tribunal can balance the competing interests without one.

The sincerity of the first prosecutor’s safety concern changes nothing, because the text conditions relief on an order of the tribunal and not on the prosecutor’s own assessment of risk. The duty stays in force from the moment the prosecutor knows of the mitigating information until a court says otherwise, so a prosecutor with a legitimate reason to withhold has to make the request.

Ethics Rule Versus Brady

Rule 3.8(d) requires timely disclosure of known information that tends to negate guilt or mitigates the offense, and its text asks nothing about how much the information would matter to the result.³⁰ A second disclosure duty covers much of the same ground but rests on the Due Process Clause. When the prosecutor withholds favorable evidence that could exculpate the defendant or reduce the sentence, the resulting trial fails the basic requirements of due process, provided the information is material.³¹ In Brady itself, the accused faced the death penalty for felony murder, and the prosecutor failed to disclose a co-defendant’s statement admitting that the co-defendant, not Brady, had done the actual killing. The Court overturned the sentence.³²

Neither duty depends on a defense request. The constitutional duty applies whether or not the defense asks, because the specificity of the defense request does not change the prosecutor’s obligation,³³ and the text of the ethics rule never mentions a request. The constitutional duty also sets no particular delivery date: Brady did not require disclosure at a particular time, so long as the defense receives the evidence in sufficient time to use it at trial.³⁴

The constitutional duty also reaches beyond evidence that points to innocence. As Giglio shows, impeachment evidence, which undercuts a witness’s credibility, falls within it: the undisclosed promise of non-prosecution went to the one witness on whom the government’s case depended almost entirely, and the jury was entitled to know of it.³⁵ The extension matters because many convictions rest on the testimony of co-defendants and informants who receive or expect benefits for testifying, and knowing those benefits can be the most important part of the defense attack on the witness’s credibility.³⁶

What separates the constitutional duty from the ethics rule is materiality. Brady did not say how material the withheld evidence must be; that question was left to later cases, beginning with United States v. Bagley.³⁷ Under the standard that emerged, information is material if there is a “reasonable probability” that, had it been disclosed, the outcome of the trial or sentencing would have been different. The defendant need not show that a different outcome was “more likely than not”; enough doubt to “undermine confidence in the outcome” suffices.³⁸ Smith v. Cain states the same test: reversal follows if “the likelihood of a different result is great enough to ‘undermine[ ] confidence in the outcome of the trial.’”³⁹ The defendant is also spared the severe burden of showing that newly discovered evidence probably would have resulted in acquittal.⁴⁰ Three features of the standard, drawn from Kyles and Agurs, show how a court applies it:

The test is not one of sufficiency, so the defendant need not show that the remaining evidence would have been too thin to convict; it is enough that the favorable evidence could reasonably be taken to put the whole case in such a different light as to undermine confidence in the verdict.⁴¹
The test looks at the suppressed evidence collectively, so a court asks whether all the withheld items together undermine confidence in the outcome and does not require each item to clear the bar alone.⁴²
The test disregards the prosecutor’s state of mind, because when suppression produces constitutional error it is because of the character of the evidence and not the character of the prosecutor.⁴³

Materiality belongs in the constitutional rule because of when and by whom it is applied. After trial a judge asks whether the nondisclosure denied the defendant a fair trial, and unless it did, the prosecutor has not violated the constitutional duty.⁴⁴ Agurs explained why a looser test will not do: a standard that required disclosure of anything that might affect the jury’s verdict approaches the “sporting theory of justice” that Brady rejected, because if everything that might influence a jury had to be disclosed, the only way to comply would be complete discovery of the prosecutor’s files as routine practice.⁴⁵ The ethics rule speaks at a different moment. It addresses the prosecutor before trial, when an item’s significance can seldom be predicted until the record is complete.⁴⁶ Leaving out a materiality screen takes the prediction away from a lawyer who has already concluded that the defendant is guilty and hands the item to the defense, which can decide what use to make of it.⁴⁷

The textual difference follows from that reasoning. The prosecutor’s constitutional duty is limited to evidence material to guilt or punishment, while the ethics rule does not expressly include a materiality requirement, which makes the ethical standard somewhat broader.⁴⁸ The Supreme Court noticed a version of that gap in Kyles: the Brady rule requires less of the prosecution than the ABA Standards for Criminal Justice, which call generally for disclosure of any evidence tending to exculpate or mitigate, and the Court has never held that the Constitution demands an open-file policy.⁴⁹

The broader text has not produced a stricter standard everywhere. A majority of the few states that have addressed the question have been wary of holding prosecutors to an ethical duty of disclosure that differs from the standard under the Constitution or court rule.⁵⁰ In those jurisdictions the ethics rule’s wider language may not independently support discipline for withholding an immaterial item. A question about what Rule 3.8(d) requires should still be answered from the rule’s text, which has no materiality filter, while a question about whether a conviction must be set aside is a constitutional one governed by materiality.

Hypothetical Illustration

In a robbery prosecution, the prosecutor knows of a police note recording that a customer thought the robber had a short beard. The defendant was clean-shaven when arrested, but the store clerk, who knew the defendant by name, identified the defendant, security video showed the robber’s face, and the stolen cash was found in the defendant’s car. The note is never disclosed. After conviction, a court reviewing the omission asks whether, with all the other evidence, there is a reasonable probability of a different result, and it concludes there is not, so there is no Brady violation and no new trial. The note was still information known to the prosecutor that tends to negate guilt, and the text of paragraph (d) called for timely disclosure without any inquiry into whether it would have changed the verdict.

The promise in Giglio sits on the other side of the line. It went to the witness on whom the government’s case depended almost entirely, so the constitutional threshold was cleared,⁵¹ while the independent proof in the robbery case leaves no reasonable probability that the beard note changed the result. The ethics rule treats the two items alike, because it asks only whether each tends to negate guilt. The Constitution grants a new trial only for the first.

Exam Analysis Steps

Because the two duties ask different questions about the same withheld item, an exam problem is best run in a fixed order that keeps the ethics question apart from the constitutional one:

Ask whether the item is favorable to the accused, meaning that it tends to negate guilt, mitigates the offense, or impeaches a government witness.
Ask whether the prosecutor personally knew of the item. The ethics rule is limited to what the prosecutor knows, while the constitutional duty also reaches what the police and others acting for the government knew.
If the question concerns discipline, apply the text of the rule: a favorable item known to the prosecutor had to be disclosed in a timely way whatever its likely effect on the outcome.
If the question concerns setting aside the conviction, ask whether the suppressed items, taken together, create a reasonable probability of a different result sufficient to undermine confidence in the verdict, without regard to the prosecutor’s good or bad faith.

Step three is where the ethics rule is tested and step four is where Brady is tested, and an answer that imports a materiality inquiry into step three misreads the rule’s text. A prosecutor accused of violating paragraph (d) therefore cannot defend by arguing that the withheld item would not have changed the verdict, although that same argument may defeat a request for a new trial. The reverse also holds: a conviction that survives a Brady challenge for want of materiality leaves untouched the separate question whether the prosecutor breached the ethics rule.

Agurs and Kyles converge on advice that serves both duties. Because the significance of an item can seldom be predicted accurately until the entire record is complete, “the prudent prosecutor will resolve doubtful questions in favor of disclosure.”⁵² Kyles adds that the prosecution, which alone can know what is undisclosed, must gauge the likely net effect of all such evidence and disclose when the point of “reasonable probability” is reached.⁵³ The advice protects the prosecutor under both regimes. An item handed to the defense can produce neither a reversal nor a charge of nondisclosure, while an item withheld on a prediction is safe only if the prediction proves right and a reviewing court agrees. Because the ethics rule has no materiality screen, no prediction about an item’s weight can guarantee safety from discipline, and disclosure of the doubtful item is the course both the rule’s text and the cases favor.