United States v. Mack: High Bar for Franks Hearings and Flexible “Substantial Compliance” with Ronder in Jury Note Readbacks

Court: United States Court of Appeals for the Second Circuit
Case: United States v. James Mack (a/k/a “Kiko”) — Nos. 24‑603‑cr (L), 24‑618‑cr (Con)
Date: November 19, 2025
Disposition: Judgment of conviction AFFIRMED (Summary Order)

Important Note: This is a summary order. Under Federal Rule of Appellate Procedure 32.1 and Second Circuit Local Rule 32.1.1, it is citable but has no precedential effect. It is thus persuasive, not binding, authority.

I. Introduction

This appeal in United States v. Mack arises from a federal narcotics and firearms prosecution tied to street-level drug trafficking in Syracuse, New York. James Mack was tried and convicted by a jury for:

Possession with intent to distribute cocaine and cocaine base (crack), under 21 U.S.C. § 841(a)(1), (b)(1)(B), and (b)(1)(C) (the opinion mistakenly cites Title 18, but the substantive drug statute is in Title 21).
Possessing a firearm in furtherance of a drug trafficking crime, under 18 U.S.C. § 924(c)(1)(A)(i).
Being a felon in possession of a firearm, under 18 U.S.C. §§ 922(g)(1) and 924(a)(2).

The evidence against Mack stemmed from an investigation by the Syracuse Police Department (“SPD”) that relied heavily on a confidential informant (“CI”) and culminated in a search warrant for Mack’s residence and vehicles. The search of one of those vehicles, a Honda Accord, revealed narcotics, a firearm, and cash concealed in a hidden compartment or “trap.”

Mack’s appeal focused on two principal issues:

Denial of a Franks hearing. Mack alleged that the warrant affidavit contained false or misleading statements regarding the CI’s reliability and that the district court erred in denying his request for an evidentiary hearing under Franks v. Delaware, 438 U.S. 154 (1978).
Handling of a jury note. During deliberations, the jury requested testimony readbacks regarding the sequence of events involving Mack’s use of the Accord and the size of the trap. Mack challenged the district court’s procedure and substance in responding to this note, arguing noncompliance with the Second Circuit’s framework in United States v. Ronder, 639 F.2d 931 (2d Cir. 1981), and that fairness required reading back the cross-examinations of the relevant officers.

The Second Circuit affirmed the district court in all respects. Although the court issued only a summary order, the decision offers useful, citable guidance on two recurring procedural issues in criminal practice:

How high the bar remains for defendants seeking a Franks hearing when challenging search warrant affidavits, and
How flexibly the “Ronder procedure” for handling jury notes can be applied under the rubric of “substantial compliance.”

II. Summary of the Opinion

A. Background and Procedural History

In February 2020, after several months of investigation assisted by a confidential informant, SPD obtained a search warrant for Mack’s residence and vehicles. When officers executed the warrant the next day, they discovered:

Cocaine and crack cocaine;
Marijuana;
A loaded .38 caliber Charter Arms revolver; and
$2,900 in cash,

all found in a hidden compartment (“trap”) in Mack’s Honda Accord, which was registered to him. These discoveries formed the backbone of the federal prosecution.

Following his indictment, Mack moved to suppress the evidence derived from the search, alleging defects in the warrant affidavit. Specifically, he sought a Franks hearing to challenge statements about the CI’s reliability. The district court denied that request and admitted the evidence.

At trial in October 2022, a jury convicted Mack on all three counts. The district court sentenced him to 180 months’ imprisonment and eight years of supervised release. Mack timely appealed.

B. Main Holdings

The Second Circuit rejected both of Mack’s principal appellate claims:

No entitlement to a Franks hearing. Mack failed to make the required “substantial preliminary showing” that the affidavit contained material false statements about the CI’s reliability made knowingly, intentionally, or with reckless disregard for the truth. Even assuming arguendo some inaccuracy about the timing of the CI’s work, the allegedly false statements were not material to probable cause, because the remaining content of the affidavit independently established a fair probability that evidence of drug trafficking would be found in Mack’s apartment and vehicles.
Substantial compliance with Ronder; no abuse of discretion in jury-note response. The district court substantially complied with the procedural requirements for responding to jury notes articulated in Ronder. Substantively, it reasonably interpreted the jury’s request as calling only for the direct testimony of the two detectives and therefore acted within its discretion by reading back only their direct examinations, while inviting the jury to request anything further if needed.

Accordingly, the Second Circuit affirmed Mack’s convictions and sentence.

III. Detailed Analysis

A. The Franks Hearing Issue

1. Legal Framework: What Must a Defendant Show to Get a Franks Hearing?

The Supreme Court in Franks v. Delaware, 438 U.S. 154 (1978), created a narrow but important avenue for challenging the veracity of a search warrant affidavit. A defendant is not automatically entitled to an evidentiary hearing merely because he alleges that the affidavit is false or misleading. Instead, he must meet a demanding threshold showing.

The Second Circuit summarized this standard (quoting its recent decision in United States v. Sandalo, 70 F.4th 77 (2d Cir. 2023)):

To obtain a Franks hearing, “a defendant must make a substantial preliminary showing of (1) falsity, that a false statement was included by the affiant in the warrant affidavit, (2) knowledge, that the affiant made the allegedly false statement knowingly and intentionally, or with reckless disregard for the truth, and (3) materiality, that the allegedly false statement is necessary to the finding of probable cause.”

These three components—falsity, knowledge/recklessness, and materiality—are each essential. If the defendant fails on any one, no hearing is required.

On the probable cause question, the court invoked United States v. McKenzie, 13 F.4th 223 (2d Cir. 2021), for the familiar standard:

[Probable cause exists where] there is a “fair probability that contraband or evidence of a crime will be found in a particular place.”

On appeal, the court’s review splits along the components of the Franks analysis (per Sandalo):

Factual findings of falsity and knowledge are reviewed for clear error.
Materiality—whether, excising the challenged statements, the affidavit still supports probable cause—is reviewed de novo.

2. Mack’s Argument: Alleged Inconsistency with a State Darden Hearing

Mack’s challenge centered on statements in the SPD detective’s affidavit regarding the CI’s reliability. He contended that the affidavit effectively represented that the CI had been a proven, reliable informant based on “prior police investigations” and “numerous controlled buys” before the investigation into Mack began in August 2019. He argued that this representation was contradicted by findings in a state-court proceeding.

In a parallel state prosecution, Mack obtained a hearing under People v. Darden, 34 N.Y.2d 177 (1974), the New York procedure for testing the existence and reliability of a confidential informant in an in camera (non-public) setting designed to protect the CI’s identity. There, a judge reported that the CI first began providing information to SPD about illegal narcotics sales in August 2019.

Mack read this as establishing that the CI could not have had a history of prior reliable controlled buys before August 2019. He therefore asserted that the federal warrant affidavit contained knowingly or recklessly false statements about the CI’s reliability, justifying a Franks hearing and potentially suppression of the fruits of the search.

3. The Court’s Reading of the Affidavit: No Actual Inconsistency

The Second Circuit rejected Mack’s characterization of the affidavit as a misrepresentation. The affidavit, submitted on February 11, 2020, stated that the CI:

“has been verified through prior police investigations which resulted in numerous controlled buys”, and
“has been providing investigative information to members of the [SPD] . . . for several months.”

The court construed this language to mean simply that, by the time the affidavit was sworn in February 2020, the CI had engaged in “prior police investigations” and “numerous controlled buys” that established his reliability. That is, the “prior” in “prior police investigations” refers to investigations that were prior to the affidavit, not necessarily prior to August 2019.

Critically, the affidavit also indicated that the SPD’s investigation into Mack began with a tip from the CI in August 2019. But the affidavit did not say that the CI was considered reliable from the first day he provided information. As the court put it:

While the affidavit states that the investigation into Mack began upon receiving a tip from the CI in August 2019, it does not state that the SPD had deemed the CI credible from the outset of his cooperation.

Thus, there is no inconsistency between:

The state court’s finding that the CI first provided information in August 2019; and
The affidavit’s assertion that, by February 2020, the CI had been verified as reliable through prior investigations and controlled buys and had been providing information “for several months.”

Put differently, the affidavit can be read as saying: From August 2019 onward, and in the months leading up to February 2020, the CI participated in investigations and controlled buys that demonstrated his reliability. This reading harmonizes the state and federal records and undermines Mack’s claim of falsity.

4. Materiality: Probable Cause Without the Contested Statements

The panel went further, explaining that even if one accepted Mack’s interpretation and assumed the affidavit could be read as falsely implying pre–August 2019 cooperation, Mack still would not be entitled to a Franks hearing. Why? Because the alleged misrepresentation was not material to probable cause.

The court emphasized that, even striking the contested statements about the CI’s pre‑August reliability, the affidavit contained ample independent evidence to support probable cause:

Two controlled buys directly involving Mack. The affidavit described two specific controlled purchases of cocaine from Mack that the SPD arranged and supervised. During these buys:
- Officers observed Mack leave his apartment.
- He entered his Honda Pilot, drove within the apartment complex parking lot to where his Honda Accord was parked, and parked the Pilot next to the Accord.
- He then entered the Accord, returned to the Pilot, and drove away to meet the CI for the controlled buy.
- After the first controlled buy, officers followed him back to his apartment building.
Evidence that the Accord was used as a stash vehicle. The detective’s observations reasonably suggested that Mack was using the Accord as a “stash” for narcotics—leaving his apartment, accessing the Accord, and then immediately going to consummate a drug sale.
Mack’s prior drug trafficking convictions. The affidavit recounted Mack’s criminal history, including multiple prior convictions for selling drugs, which can factor into a probable cause analysis when combined with current suspicious activity.

Taking these facts together, the court held that the affidavit would still establish probable cause to search Mack’s apartment and vehicles even if the contested statements were excised. The case thus failed on the materiality prong of Franks regardless of any ambiguity about timing.

5. Result: No “Substantial Preliminary Showing” and No Franks Hearing

Because Mack neither (a) established actual falsity of the CI‑reliability language, nor (b) showed that any assumed falsity was material to probable cause, he did not meet the “substantial preliminary showing” required by Franks and Sandalo. Accordingly, the district court’s denial of a Franks hearing was affirmed.

B. The Jury Note and the Ronder Procedure

1. The Jury’s Request

During deliberations, the jury sent a written note requesting:

“the testimony of [O]fficer Ripley concerning the order of events getting into the [A]ccord as well as Officer Cowan's testimony of his surveillance and the order of events getting to the [A]ccord[,]" and for "clarity on the size of [the] trap[.]”

Both Detectives Ripley and Cowan had testified to Mack’s movements between his apartment, his Honda Pilot, and the Honda Accord, as well as the hidden compartment in the Accord that ultimately contained drugs, a firearm, and cash.

The district court responded by having the direct examinations of both detectives read back to the jury. Only afterward, at sidebar, did the court solicit the parties’ views and rejected Mack’s request that the relevant cross-examinations also be read.

On appeal, Mack argued both:

Procedural error: that the court failed to properly follow the procedural steps required by Ronder, and
Substantive error: that limiting the readback to direct testimony unfairly highlighted the prosecution’s narrative and omitted impeachment material developed on cross, thereby abusing the court’s discretion.

2. The Ronder Framework and “Substantial Compliance”

United States v. Ronder, 639 F.2d 931 (2d Cir. 1981), sets forth a four‑step procedure for handling jury notes, particularly when they seek substantive guidance or readbacks:

The jury inquiry must be submitted in writing.
The note should be marked as a court exhibit and read into the record in the presence of counsel and the defendant before the jury is recalled.
Counsel must be afforded an opportunity to suggest appropriate responses before the jury is recalled.
After the jury is recalled, and in its presence, the judge should read the note into the record before giving a response.

However, the Second Circuit has emphasized that substantial compliance with this procedure suffices; rigid adherence to the precise sequence is not always required. In United States v. Ulloa, 882 F.2d 41 (2d Cir. 1989), the court noted:

“[M]indful that trial judges must be permitted some latitude in determining how best to handle jury inquiries, we have accepted substantial compliance with the Ronder procedure.”

3. Procedural Analysis: Did the District Court Substantially Comply?

The Second Circuit concluded that the district court substantially complied with Ronder’s requirements:

Written inquiry: The jury’s question was submitted in writing, satisfying the first Ronder step.
Note read into record: The court read the note into the record with both parties and the jury present and later docketed it, thereby satisfying the purpose of the second requirement: to ensure the defendant knows the contents of the note and to create an adequate appellate record.
Opportunity to be heard: Although the court did not invite suggestions before the direct testimony was read back, it did give both sides an opportunity afterward to propose supplements, including Mack’s request to add cross-examination portions, before the jury resumed deliberations. In the panel’s view, this opportunity satisfied the core concern of the third Ronder requirement—affording counsel a meaningful chance to be heard.
Note read before response: The court read the note into the record in open court, in the presence of the jury, satisfying the fourth step in substance.

The opinion expressly recognized that the timing of counsel’s input could be more consequential in other cases—particularly where counsel might object to any readback at all. The court left open that, on different facts, substantial compliance might demand the opportunity for input before any response is given. But in this case, where Mack only sought to supplement an otherwise unobjectionable readback, the post‑readback sidebar sufficed.

Thus, procedurally, the court held that the district judge did not commit reversible error under Ronder.

4. Substantive Analysis: Limiting the Readback to Direct Examination

Substantively, the question was whether the district court abused its discretion by reading only the direct testimony of the two officers and not also their cross-examinations. The standard of review comes from cases like United States v. Khalupsky, 5 F.4th 279 (2d Cir. 2021): the appellate court asks whether the trial judge gave a reasonable interpretation to the jury’s request and whether the response risked undue emphasis or unfairness.

The court concluded that there was no abuse of discretion:

The jury’s note specifically asked for Ripley’s “testimony … concerning the order of events getting into the Accord” and Cowan’s “testimony … of his surveillance and the order of events getting to the Accord,” plus clarity on the trap’s size.
The district court reasonably interpreted this request as seeking the officers’ initial narrative descriptions of those events—i.e., their direct testimony—rather than the entire back-and-forth of cross-examination.
While the court acknowledged that it might have been “more prudent” to also read relevant cross-examination portions, prudence is not the standard; the question is whether the judge’s interpretation and response were reasonable.
The district court also took a protective step by explicitly telling the jury to “let us know if there’s anything else you need.” The jury did not ask for further testimony, which the panel treated as implicit confirmation that the jury received what it had requested.

On these facts, the panel held that the judge’s decision to limit the readback to the direct examinations fell within the permissible range of discretion.

5. Support from United States v. McElroy

The opinion drew an analogy to United States v. McElroy, 910 F.2d 1016 (2d Cir. 1990). In McElroy:

The jury requested “[the defendant’s] testimony,” later clarifying it wanted the “cross‑examination portion.”
The trial judge provided the government’s cross-examination of the defendant, then asked the jury if that was what they wanted. The jury confirmed it was.
A co-defendant argued that the co-defendant’s cross-examination of the same witness should also be read back, but the judge refused.

The Second Circuit affirmed in McElroy, holding that because the jury had confirmed it wanted the government’s cross, the judge reasonably interpreted the note and acted accordingly.

Applying the same reasoning, the court in Mack noted that the district judge had reasonably interpreted the jury’s request here as seeking only the direct narrative testimony, and that the jury’s silence after the readback, despite an invitation to request more, confirmed the adequacy of that response.

IV. Precedents and Authorities Discussed

A. Franks v. Delaware, 438 U.S. 154 (1978)

Franks established that a defendant may, in limited circumstances, challenge the truthfulness of statements in a warrant affidavit. To justify an evidentiary hearing, the defendant must show:

A deliberate or reckless falsehood (or omission) by the affiant; and
That this falsehood or omission was material to probable cause.

If a hearing is granted and the defendant proves these elements, and if the affidavit, without the false material, no longer establishes probable cause, the warrant and its fruits must be suppressed.

B. United States v. Sandalo, 70 F.4th 77 (2d Cir. 2023)

Sandalo is a recent Second Circuit elaboration on the Franks standard. The court in Mack quotes Sandalo’s three‑pronged formulation (falsity, knowledge/recklessness, and materiality) and adopts its division of appellate review into clear-error and de novo components.

C. United States v. McKenzie, 13 F.4th 223 (2d Cir. 2021)

McKenzie is cited for the general definition of probable cause: a “fair probability” that contraband or evidence of a crime will be found. The case underscores that probable cause is a pragmatic, common-sense standard, not a rigid rule demanding proof beyond a reasonable doubt.

D. People v. Darden, 34 N.Y.2d 177 (N.Y. 1974)

Darden is a New York Court of Appeals decision creating a procedure for in camera review of confidential informants as a way to balance the defendant’s right to challenge the existence and reliability of an informant against the state’s interest in protecting the informant’s identity and safety.

In Mack, the state court’s Darden hearing produced a factual finding about when the CI first began providing information (August 2019). Mack tried to leverage that finding to create a conflict with the federal affidavit, but the Second Circuit found no inconsistency.

E. United States v. Ronder, 639 F.2d 931 (2d Cir. 1981)

Ronder articulates a detailed protocol for handling substantive jury notes, particularly in criminal trials. It serves to:

Ensure transparency and fairness;
Give defense and prosecution counsel a chance to influence the court’s response; and
Create an adequate record for appellate review.

The Mack panel applies Ronder not as a rigid checklist but through the lens of substantial compliance.

F. United States v. Ulloa, 882 F.2d 41 (2d Cir. 1989)

Ulloa is cited for the principle that substantial, not perfect, compliance with Ronder will often suffice. It recognizes that trial judges need flexibility and that appellate courts should not overturn convictions for minor deviations absent actual prejudice or a significant risk of misunderstanding the jury’s inquiry.

G. United States v. Khalupsky, 5 F.4th 279 (2d Cir. 2021)

Khalupsky provides the standard of review for a district court’s interpretation of jury notes and decisions about readbacks: abuse of discretion, with the focus on whether the judge’s interpretation was “reasonable.” The Second Circuit in Mack invokes this “reasonable interpretation” standard in approving the limited readback.

H. United States v. McElroy, 910 F.2d 1016 (2d Cir. 1990)

McElroy is used as a close analog supporting the Mack court’s conclusion that limiting a readback to the testimony the jury confirmed it wanted is permissible. It illustrates that the court will defer to a trial judge’s reasonable interpretation of a jury’s note, especially when the jury signals satisfaction with the response.

V. Clarification of Key Legal Concepts

A. Franks Hearing

A Franks hearing is a specialized evidentiary hearing at which a defendant may challenge the veracity of the statements in a warrant affidavit. It is not granted automatically; the defendant must first make a “substantial preliminary showing” that:

The affiant (usually a law enforcement officer) included a false statement, or omitted critical information, in the affidavit;
The falsehood or omission was deliberate or reckless, not just a mistake; and
Without that falsehood or with the omitted facts included, the affidavit would lack probable cause.

Only if this showing is made does the court hold a live hearing where the affiant may be cross‑examined and other evidence presented. The remedy, if the defendant ultimately prevails, is suppression of evidence obtained under the defective warrant.

B. Probable Cause

Probable cause is a flexible, commonsense standard. For a search warrant, it requires a “fair probability” that evidence of a crime will be found in the place to be searched, based on the totality of the circumstances. It is less than a preponderance of the evidence and far below proof beyond a reasonable doubt.

In Mack, the court concluded that:

Direct police observations of Mack’s behavior during controlled buys;
The pattern of moving between his residence, his Honda Pilot, and the Honda Accord; and
His history of drug convictions

together easily met the probable cause standard for searching his apartment and vehicles, regardless of any dispute about how “seasoned” the CI was.

C. Confidential Informant (CI) and Controlled Buys

A confidential informant is someone—often facing charges or seeking leniency—who provides information to law enforcement about criminal activity. The CI’s reliability is crucial; courts examine how long the CI has worked with law enforcement, whether previous tips were corroborated, and whether the CI has participated in verified “controlled buys.”

A controlled buy is a drug purchase supervised by law enforcement, typically involving:

Search of the CI before the buy to ensure no contraband;
Providing marked bills or recording devices;
Surveillance of the CI’s movements; and
Post-buy recovery and testing of the purchased substances.

Such operations can both test the CI’s reliability and develop probable cause against the target.

D. Hidden “Trap” Compartments

A trap in the context of narcotics trafficking is a concealed compartment in a vehicle or structure used to hide contraband, weapons, or money. The existence and characteristics of a trap (e.g., size, location, method of operation) can be probative of drug trafficking, particularly when coupled with other evidence such as controlled buys and surveillance.

E. Standards of Appellate Review

Clear error: The appellate court defers heavily to the district court’s factual findings and will overturn them only if left with a “definite and firm conviction” that a mistake has been made.
De novo: The appellate court gives no deference and decides the legal issue from scratch (e.g., whether, as a matter of law, an affidavit—minus challenged statements—establishes probable cause).
Abuse of discretion: The appellate court asks whether the trial judge’s decision falls outside the range of acceptable choices. If reasonable judges could disagree, the ruling stands.

In Mack, these standards are applied to the factual and legal components of the Franks analysis and to the district court’s handling of the jury note.

F. Non‑Precedential Summary Orders and FRAP 32.1

A summary order in the Second Circuit is a short, often fact‑specific decision that the court deems not to have precedential value. Under FRAP 32.1 and Local Rule 32.1.1:

Summary orders filed after January 1, 2007, may be cited in any court in the United States.
Their citation is permitted but they have no precedential effect in the Second Circuit. They may, however, be considered persuasive.
When cited, parties must identify them as “SUMMARY ORDER” and serve copies on any pro se litigant.

Mack falls into this category: it does not formally bind future Second Circuit panels but can be cited as persuasive authority, especially on recurring procedural issues like Franks showings and Ronder compliance.

VI. Practical and Doctrinal Impact

A. For Defense Counsel: Reinforced Stringency of Franks Threshold

Even though Mack is a summary order, it underscores how demanding the Franks threshold remains in the Second Circuit.

Ambiguous or debatable language isn’t enough. Mack attempted to leverage a perceived inconsistency between a state Darden finding and federal affidavit language. The court resolved that ambiguity by harmonizing the records in a way that preserved the affidavit’s truthfulness. Defense counsel should be prepared to show not just tension in wording, but clear falsity or deception.
Materiality is decisive. Even where there is some colorable falsehood, counsel must demonstrate that, without the misstatement, the affidavit would lack probable cause. Here, robust independent evidence—controlled buys, surveillance, and criminal history—made it impossible to show materiality. This suggests that attacks on CI veracity may be less fruitful where law enforcement has corroborated behavior through direct surveillance and controlled operations.
State evidentiary rulings have limited leverage. Mack’s reliance on a state Darden report illustrates a common strategy: using state findings to attack federal affidavits. Mack shows that unless the state findings unequivocally contradict the affidavit, federal courts may reconcile the two and find no falsehood.

B. For Prosecutors and Law Enforcement: Drafting Affidavits with an Eye to Franks

From the government’s perspective, Mack reinforces several best practices:

Corroborate CIs with direct evidence. SPD’s surveillance and controlled buys were central to the court’s probable cause analysis. Investigations that do not overly rely on uncorroborated CI statements are much more resistant to Franks challenges.
Use careful, temporally accurate language. The affidavit’s wording—“has been verified through prior police investigations” and “has been providing … for several months”—was sufficiently precise and flexible to avoid contradiction with later state findings. Affidavits should avoid unnecessary specificity that could later be attacked as inaccurate, and should be scrupulously honest about timelines.
Include prior convictions judiciously. While prior bad acts cannot substitute for proof of current criminal conduct, in probable cause determinations they can corroborate present suspicions. Here, Mack’s prior drug dealing convictions supported the inference drawn from his observed activity during the controlled buys.

C. For Trial Judges: Managing Jury Notes with Flexibility but Transparency

Mack also provides guidance to trial courts on how to manage jury requests:

Substantial compliance is acceptable. The Second Circuit does not insist on wooden adherence to the exact sequencing in Ronder so long as the core purposes—transparent communication, meaningful opportunity for counsel input, and a clear record—are served.
Timing of counsel’s input matters contextually. The panel candidly acknowledged that, in other fact patterns (for example, where defense counsel would oppose any readback at all), denying pre‑response input could be problematic. But where counsel’s concern is about supplementing an otherwise acceptable response, a post‑response sidebar may be adequate.
Invite follow‑up requests. The judge’s practice of telling the jury to “let us know if there’s anything else you need” proved important. It both protected the record and allowed the appellate court to infer that the jury was satisfied.
Reasonable interpretation of jury notes is key. Following Khalupsky and McElroy, Mack confirms that judges have discretion to interpret jury requests and that appellate courts will defer so long as the interpretation is reasonable and does not distort the balance of the evidence.

D. For Appellate Practice: Preserving and Framing Jury‑Note Issues

For appellate lawyers, Mack illustrates the importance of:

Creating a record at sidebar. Even though the judge had already begun to respond to the jury note, defense counsel’s request at sidebar for inclusion of cross-examination testimony preserved the substantive fairness issue for appeal.
Linking procedural missteps to prejudice. Merely cataloguing deviations from Ronder rarely suffices; counsel must show how the timing or content of the court’s response realistically risked distorting the jury’s deliberations.

E. Doctrinally: No New Rule, but Reinforcement of Existing Principles

As a summary order, Mack does not alter binding doctrine. Rather, it:

Confirms the robustness of the existing Franks/Sandalo framework and emphasizes the importance of the materiality requirement.
Reinforces that Ronder demands transparency and opportunity for input but tolerates flexibility in implementation so long as “substantial compliance” is achieved.
Illustrates again that appellate review of both Franks determinations and jury‑note responses is highly deferential to district courts on factual and discretionary matters.

VII. Conclusion

United States v. Mack is a nonprecedential but instructive Second Circuit decision that crystallizes two important themes in criminal procedure:

The high threshold for Franks hearings. Defendants must do more than find arguable inconsistencies or ambiguities; they must show deliberate or reckless falsehoods that are genuinely necessary to the probable cause finding. Where law enforcement has corroborated a CI’s tips with controlled buys and surveillance, Franks challenges will be particularly difficult to sustain.
The flexible, context‑dependent application of Ronder’s jury‑note procedures. Trial judges retain discretion to reasonably interpret jury requests and to tailor readbacks accordingly, provided that counsel are meaningfully heard, the record is clear, and the jury is afforded an opportunity to request more if needed. Minor deviations from ideal sequencing will not warrant reversal absent prejudice or unreasonable handling.

Although Mack carries no precedential weight, practitioners in the Second Circuit can expect it to be cited as persuasive authority—especially in cases involving:

Challenges to warrant affidavits based on CI reliability;
Arguments about the threshold for Franks hearings;
Disputes over whether trial courts properly responded to jury notes; and
Claims that readbacks unduly emphasized one side’s evidence.

In the broader legal landscape, Mack exemplifies the Second Circuit’s continued deference to district court fact‑finding and case management, and its insistence that suppression of evidence and reversal of convictions be reserved for serious, outcome‑affecting errors, rather than technical imperfections or debatable interpretive choices.