Brady Evidence Suppression Claims: Should Courts Require Criminal Defendants to Exercise Due Diligence during Discovery?  

Author: Maxel Moreland, Associate Member, University of Cincinnati Law Review

When a criminal defendant enters a court room, the court controls the future of that defendant’s liberty. With so much at stake, criminal trial procedures should not require criminal defendants to exert additional effort in procuring beneficial evidence when the prosecutor has already discovered such beneficial evidence. Juries, when determining the guilty status of the accused, must find criminal defendants guilty beyond a reasonable doubt. However, determination of guilt can be difficult when the jury cannot review key evidence.

The seminal Supreme Court case, Brady v. Maryland, created obligations for prosecutors to disclose evidence favorable to criminal defendants.[1] However, jurisprudence stemming from that case has eroded the ability to successfully raise a Brady claim, particularly in light of the emergence of the “due diligence rule” in lower federal courts.[2] The Supreme Court recently declined to hear a case which would have clarified whether the due diligence rule, which obligates a criminal defendant to exercise due diligence to obtain evidence themselves, should apply in subsequent Brady cases.[3] Abandonment of the due diligence rule would promote the general purpose of Brady, the fairness of criminal trials, and the effectiveness of our justice system.

Purpose of Brady

In Brady, the Supreme Court established that a due process violation occurs when prosecutors suppress evidence favorable to a criminal defendant when that evidence is material to proving guilt or determining punishment.[4] The Court attempted to fix discriminatory practices against criminal defendants by extending previous rulings, which focused on remedying prosecutorial misconduct.[5] The principle purpose behind these rulings is to ensure that juries can review important evidence, beneficial to criminal defendants, before determining the guilt of a criminal defendants.[6] The Court reasoned that allowing prosecutors to withhold potentially exculpatory evidence would be a disservice to both criminal defendants and society as a whole.[7]

Originally, Brady claims required the criminal defendant to request evidence from the prosecutor before the evidence was considered suppressed.[8] However, later cases determined that the government was not free from its obligation to disclose evidence simply because the defendant did not properly ask for it.[9] The Court has noted numerous instances in which a prosecutor could take advantage of defense requests and limit the effect of Brady.[10] The government has an obligation to grant criminal defendants a fair trial and must volunteer evidence that, if otherwise suppressed, would significantly impact their trial.[11] Decades later, in U.S. v. Bagley, the Court removed distinctions between exculpatory evidence and evidence used to impeach and determined that the government violates the due process clause when it does not disclose evidence favorable to criminal defendants, regardless of a request.[12]

Brady was meant to promote the interest of societal justice by preventing prosecutors from suppressing exculpatory or impeaching evidence. The main purpose of criminal trials is to determine the guilt or innocence of the accused through the use of evidence.[13] Withholding exculpatory or other favorable evidence does not promote this purpose. Instead, suppression of evidence hinders a jury’s ability to determine a defendant’s guilt as the jury misses out on potentially key information.

Development of Due Diligence Rule

While most circuit courts apply a due diligence rule, every circuit does not apply due diligence rule uniformly.[14] The general rule is that the government does not have to disclose evidence if the defendant either knows about the evidence or should have known how to obtain the evidence.[15] The rule has three major variations that diminish the prosecutorial burden to disclose: when evidence is equally available to prosecutors and defendants (typically public records); when the defendant knew about evidence and should have told his attorney; and when evidence is inaccessible to criminal defendants, but the defendant has access to the relevant facts related to the evidence.[16]

Lower courts created each variation of the due diligence rule through expansion of the phrase, “unknown to the defense,” to include evidence that the defendant should have previously known.[17] While the circuit courts apply the due diligence rule, the standards regarding how diligent a defendant must be are inconsistent. The Sixth Circuit has applied the due diligence rule to require criminal defendants to independently discover exculpatory evidence that the government failed to disclose if that evidence is available from some alternative source.[18] The Fifth Circuit applied the due diligence rule to prevent a Brady claim when impeachment evidence exists in a source where a reasonable defendant would have looked.[19] The Third Circuit has held that the government does not have an obligation to disclose evidence that a defendant could have obtained from other sources using reasonable diligence.[20] Each of these standards requires the criminal defendant to discover evidence on their own but does not provide a rationale for why the defendant needs to exercise due diligence.

While the Supreme Court has not decided on the validity of the due diligence rule, the Court has alluded to possibly barring use of the due diligence rule. In Banks v. Dretke, the Court reviewed a procedural issue involving the defendant’s inability to previously raise a Brady claim in a habeas relief petition.[21] The Court did not reject the due diligence rule, but it disparaged the concept of an evidence rule where “prosecutor may hide, defendant must seek.”[22] In the interest of due process, prosecutors have an obligation to not use deceitful tactics or partake in unjustified concealment to achieve convictions.[23] The Sixth Circuit has since relied on Banks dicta to call for an abandonment of the due diligence rule, requiring the prosecutor to disclose any uncovered exculpatory, beneficial, or impeachment evidence.[24]

Impracticable: Defendant’s Unjust Burden in Exercising Due Diligence

Prosecutors are meant to act as agents of the court through the promotion of public justice, but often justice is not served due to the adversarial nature of litigation.[25] Obligating criminal defendants to exercise due diligence to discover evidence known by prosecutors is not only burdensome because of the limited resources available to the defense but also because Brady can only be effective when prosecutors act in good faith to disclose evidence.[26]

Circuit courts have permitted the continued use of the due diligence rule, allowing prosecutors to suppress evidence under the belief that criminal defendants just need to exercise minimal effort to obtain exculpatory evidence.[27] However, this creates an undue burden on criminal defendants that do not have the same investigatory resources or experience that prosecutors enjoy. Prosecutors have access to law enforcement personnel, established investigatory funding, broad subpoena powers, and other governmental resources to assist in the discovery process.[28] Conversely, criminal defendants do not have access to these resources, especially when a defendant is represented by a court-appointed public defender.[29] Clearly, prosecutors have an advantage over criminal defendants during the discovery phase.[30] Requiring a criminal defendant to search for exculpatory or impeaching evidence that the prosecutor has already discovered creates an unnecessary burden for the criminal defendant.

Defenders of the due diligence rule argue that prosecutors should not be punished for failing to provide defendants with easily obtainable information.[31] However, to determine whether nondisclosed evidence was easily obtainable, courts must engage in a post hoc analysis of pretrial events.[32] The post hoc analysis puts the burden on the criminal defendant to prove that, even with due diligence, he could not have discovered the evidence. While prosecutors should not receive undeserved punishments, criminal defendants deserve a trial absent of prosecutorial misconduct. Requiring criminal defendants to exercise due diligence provides an additional advantage for prosecutors, at the expense of the criminally accused. This advantage allows prosecutors to justifiably engage in discovery practices that can permit suppression of exculpatory evidence. Such an allowance of unjust practices raises serious concerns about the fairness of our criminal justice system.

Alternatively, defenders of the due diligence rule argue that criminal defendants can later raise ineffective assistance of counsel (IAC) claims if their defense counsel fails to meet the due diligence obligation.[33] However, IAC claims may not always be a viable option for criminal defendants when Brady material has been suppressed. To raise an IAC claim the now-convicted inmate would have to discover the suppressed Brady material to even have a case. The criminally convicted have a difficult time discovering suppressed evidence, since most have no legal representation after conviction, and then must contend with the additional challenge of navigating their IAC claims as pro se litigants.[34] Additionally, even if the criminal defendant wins an IAC claim, it is a hollow victory when the defendant has already been subjected to an unjustified criminal sanction. Courts should not allow prosecutors the due diligence rule to relieve prosecutors merely because there is a post-conviction remedy. Using IAC as an acceptable judicial remedy to Brady violations places an undue and costly burden on criminal defendants.

Call for Supreme Court to Review Brady Due Diligence Jurisprudence

Brady was meant to protect criminal defendants from wrongful conviction or wrongful punishment and promote more just practices by prosecutors. Allowing circuit courts to continue applying the due diligence rule does not only limit the effectiveness of Brady, it effectively eliminates the force of Brady. The continued use of the due diligence rule encourages prosecutors to withhold evidence from criminal defendants, as it provides them with a justification to not disclose evidence that falls under the due diligence rule.

Due to the reliance on prosecutors to voluntary disclose Brady material, coupled with the overall inability of criminal defendants to remedy Brady violations, the due diligence rule should be abandoned. This would provide more clarity on what evidence needs to be disclosed to criminal defendants—as all exculpatory and impeachment evidence would then need to be disclosed—as well as ensure that criminal defendants have all the evidence needed to engage in a fair trial. The current use of the due diligence rule does not follow the purpose of Brady or ensure due process of law.


[1] Brady v. Maryland, 373 U.S. 83, 87 (1963).

[2] Kate Weisburd, Prosecutors Hide, Defendants Seek: The Erosion of Brady Through the Defendant Due Diligence Rule, 60 UCLA L. Rev. 138, 147 (2012).

[3] SCOTUS Won’t Tackle Brady ‘Due Diligence’ Issue, White Collar Crime Report (BNA); see U.S. v. Georgiou, 777 F.3d 125 (3rd Cir. 2015).

[4] Brady, 373 U.S. at 87 (1963).

[5] Id. at 86; see Mooney v. Holohan, 294 U.S. 103, 112 (1935) (The use of perjured testimony at trial violated the due process clause and did not comport with the basic notions of justice).

[6] Id. at 87.

[7] Id.

[8] Id.

[9] Weisburd, supra note 2 at 146.

[10] Kyles v. Whitley, 514 U.S. 419, 433 (199) (Examples include: a prosecutor failing to disclose that testimony introduced at trial was perjured, intentionally ignoring a defense request for specific evidence, and the government failing to volunteer exculpatory evidence because the evidence was either not requested by the defense or not specifically requested).

[11] Id.

[12] U.S. v. Bagley, 473 U.S. 667, 682 (1985).

[13] Weisburd, supra note 2, at 147.

[14] Weisburd, supra note 2 at 153.

[15] Id. at 154.

[16] Id. at 154-157.

[17] Id. at 150 (The phrase “unknown to defendants” was used in the Kyles analysis of Brady. In Kyles, the Court determined that prosecutors cannot suppress evidence when criminal defendants should have previously known about the evidence.).

[18] U.S. v. Mullins, 22 F.3d 1365, 1371 (6th Cir. 1994).

[19] U.S. v. Parker, 790 F.3d 550, 562 (5th Cir. 2015).

[20] Georgiou, 777 F.3d at 140.

[21] Banks v. Dretke, 540 U.S. 668, 689-90 (2004).

[22] Id. at 696.

[23] Id.

[24] U.S. v. Tavera, 719 F.3d 705, 712 (6th Cir. 2013).

[25] Gershman, supra note 30, at 558.

[26] Id. at 533.

[27] Georgiou, 777 F.3d at 140-42.

[28] Weisburd, supra note 2, at 175-76.

[29] Id. at 176 (Court-appointed attorneys and public defenders must request investigatory funds from the court and are often under-funded and overworked. The result is that most criminal defendants receive sub-par representation with lawyers that have little investigatory support).

[30] Tavera, 719 F.3d at 712.

[31] Weisburd, supra note 2, at 141.

[32] Bennett L. Gershman, Litigating Brady v. Maryland: Games Prosecutors Play, 57 Case W. Res. L. Rev. 531., 533 (2007).

[33] Weisburd, supra note 2, at 141.

[34] Weisburd, supra note 2, at 178-79.


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