Stipulation Is Not a Shield: Limited CSAM Publication and Agent Descriptions May Be Admitted Under Rule 403 to Prove Knowing Possession

1. Introduction

In United States v. Ross (1st Cir. Apr. 2, 2026), the First Circuit affirmed Kevin Lee Ross’s conviction for possessing child pornography under 18 U.S.C. § 2252A(a)(5)(B). The case arose during Ross’s supervised release following a prior child-pornography conviction (United States v. Ross ("Ross I"), 837 F.3d 85 (1st Cir. 2016)). A probation search—prompted by a tip from Ross’s brother—led to the discovery of an unauthorized cell phone in Ross’s bedroom and a laptop and external hard drive in a vehicle Ross used. A forensic examination found more than 1,380 files of CSAM across the devices.

The appeal focused narrowly on evidentiary rulings under Federal Rule of Evidence 403. Before trial, the parties entered a joint stipulation that specified nine government exhibits were “images produced by using an actual person under the age of eighteen engaging in sexually explicit conduct” and that interstate-commerce prerequisites were satisfied. Despite that stipulation:

the district court allowed the government to publish the nine CSAM exhibits to the jury (briefly and as a limited sample); and
the court allowed the forensic agent (Agent Kelly) to describe the images/clips while testifying.

Ross argued the stipulation made the exhibits non-probative and the display/description unfairly prejudicial. The First Circuit rejected both arguments, emphasizing that the government still had to prove knowing possession and that limited CSAM presentation can be probative of knowledge even where the defendant stipulates the material meets the legal definition of child pornography.

2. Summary of the Opinion

The First Circuit held that the district court did not abuse its discretion under Rule 403 by permitting (1) publication of nine representative CSAM exhibits and (2) Agent Kelly’s descriptive testimony about those exhibits. The court found the stipulation did not eliminate the exhibits’ probative value, particularly because Ross denied he possessed the devices and denied knowledge of their contents—placing scienter at issue. The panel also indicated that even if Ross had arguably failed to preserve an objection to the agent’s descriptions, his challenge failed under the more favorable abuse-of-discretion standard.

3. Analysis

3.1. Precedents Cited

A. Narrative proof, stipulations, and the government’s right to present its case

The opinion’s doctrinal anchor is Old Chief v. United States, 519 U.S. 172 (1997). The court relied on Old Chief for two linked propositions: (1) a stipulation conclusively proves the stipulated fact, but (2) the prosecution is ordinarily “entitled to prove its case by evidence of its own choice” and a defendant cannot “stipulate or admit his way out of the full evidentiary force of the case as the government chooses to present it.” Old Chief’s emphasis that “a syllogism is not a story” supports admitting evidence that supplies a coherent narrative and persuades jurors to draw necessary inferences, even when some facts are not contested.

The First Circuit treated United States v. Tavares, 21 F.3d 1 (1st Cir. 1994), and United States v. Morales-Aldahondo, 524 F.3d 115 (1st Cir. 2008), as consistent with Old Chief’s baseline rule: the government generally need not accept attempts to substitute stipulations for the prosecution’s chosen evidentiary presentation. The court also cited United States v. Dean, 135 F. Supp. 2d 207 (D. Me. 2001), for the practical point that trials need not be scrubbed of all evidence with emotional impact when the evidence is part of the government’s narrative.

B. CSAM-specific applications: stipulations do not resolve “knowing possession”

The panel treated United States v. Ross ("Ross I") as highly controlling on the Rule 403 question. In Ross I, the court upheld limited display of CSAM despite a stipulation, because Ross denied knowing possession; the displays were probative that he could not have encountered the materials without recognizing their graphic nature. The district court here explicitly relied on Ross I, and the First Circuit approved that reliance, calling the factual and legal posture “nearly identical.”

The court reinforced Ross I with United States v. Dudley, 804 F.3d 506 (1st Cir. 2015) (citing United States v. Eads, 729 F.3d 769 (7th Cir. 2013)): a defendant’s stipulation that images constitute child pornography “only went so far” where the defendant contested knowledge/possession. The cited out-of-circuit cases supported the view that representative samples and limited publication can be probative of scienter: United States v. Caldwell, 586 F.3d 338 (5th Cir. 2009), and United States v. Cunningham, 694 F.3d 372 (3d Cir. 2012). The panel also cited United States v. Long, 92 F.4th 481 (3rd Cir. 2024), emphasizing that photos/videos can communicate accuracy and detail “that words cannot duplicate,” and that probative value may decrease where evidence goes only to elements already stipulated—yet, in Ross’s case, the evidence bore on contested scienter and possession.

C. Rule 403 framework and appellate deference

The First Circuit framed Rule 403 using United States v. DiRosa, 761 F.3d 144 (1st Cir. 2014) (quoting Old Chief) for the definition of “unfair prejudice” as evidence that lures jurors to convict on an improper ground. It also invoked United States v. Varoudakis, 233 F.3d 113 (1st Cir. 2000), United States v. Rathbun, 98 F.4th 40 (1st Cir. 2024), and United States v. Carbone, 110 F.4th 361 (1st Cir. 2024) (citing United States v. Doe, 741 F.3d 217 (1st Cir. 2013)), to stress the “broad discretion” afforded trial judges in the probative-prejudice balancing and the rarity of reversal absent “extraordinarily compelling circumstances.”

D. Error standards, preservation, and harmlessness

Although the merits drove the outcome, the panel mapped the relevant review standards: preserved evidentiary objections are reviewed for abuse of discretion (United States v. Maldonado-Peña, 4 F.4th 1 (1st Cir. 2021)); even if error exists, reversal depends on whether it was harmless (United States v. García-Sierra, 994 F.3d 17 (1st Cir. 2021) (citing United States v. Brown, 669 F.3d 10 (1st Cir. 2012); and Fed. R. Crim. P. 52(a))), defined as not substantially swaying the judgment (United States v. Villa-Guillen, 102 F.4th 508 (1st Cir. 2024) (quoting United States v. Burgos-Montes, 786 F.3d 92 (1st Cir. 2015))).

For unpreserved issues, the opinion cited plain error doctrine: United States v. Leoner-Aguirre, 939 F.3d 310 (1st Cir. 2019); Fed. R. Crim. P. 52(b); and the four-part test as stated in United States v. Castillo, 158 F.4th 257 (1st Cir. 2025) (citing United States v. Encarnacion, 26 F.4th 490 (1st Cir. 2022)). On preservation specifically, the court referenced United States v. Perez-Delgado, 99 F.4th 13 (1st Cir. 2024), and United States v. Soto-Soto, 855 F.3d 445 (1st Cir. 2017), plus United States v. Perez-Cubertier, 958 F.3d 81 (1st Cir. 2020), and United States v. Ewing, 140 F.4th 1339 (11th Cir. 2025), to illustrate that generalized objections may not preserve specific evidentiary theories. Ultimately, however, the panel resolved the agent-description issue on the merits under the more forgiving standard.

3.2. Legal Reasoning

The court’s Rule 403 reasoning proceeded in three main steps:

Step 1: Identify what the stipulation did—and did not—decide

The stipulation established that the identified exhibits depicted actual minors engaged in sexually explicit conduct and that interstate-commerce predicates were met. But the offense of conviction required proof that Ross knowingly possessed material containing child pornography. The stipulation did not concede (and could not by itself prove) Ross’s possession of the devices or his knowledge of their contents.

Step 2: Connect limited publication and description to contested elements

Ross’s trial defense was that he was “set up” and that he “never used the devices.” In that posture, the government could legitimately argue that the nature and accessibility of the CSAM made ignorance implausible: limited display of representative files tended to show that a person using the devices for years would “immediately recognize” the graphic content. This is where the court treated Ross I as directly applicable: when knowledge is disputed, a stipulation that content is CSAM does not eliminate the probative force of showing (briefly and selectively) what that content actually is.

The court also emphasized that the selection—three files per device—was a small sample relative to the total volume discovered, supporting the trial judge’s conclusion that the presentation was not “needlessly cumulative” and that the probative value was not “substantially outweighed” by unfair prejudice.

Step 3: Distinguish “prejudicial” from “unfairly prejudicial”

The panel reiterated that evidence is often prejudicial by design; Rule 403 is aimed at unfair prejudice—conviction on an improper emotional basis rather than proof of the charged elements. Given the narrow quantity and the clear linkage to disputed scienter and possession, the court held that the district judge acted within the wide zone of permissible discretion.

3.3. Impact

Although the opinion is framed as an application of established doctrine rather than a doctrinal overhaul, it meaningfully clarifies (and strengthens) several practical points for future CSAM prosecutions within the First Circuit:

Stipulations to the “CSAM nature” of files will not, standing alone, bar limited publication. Where knowledge or possession is contested, courts may admit a carefully limited sample because the visceral recognizability of the material is probative of scienter.
Agent narration can survive Rule 403. Descriptions that connect files across devices (pattern/type) and help situate the forensic findings may be treated as non-cumulative narrative proof—particularly where the defense is “I didn’t know” or “I was framed.”
Quantity and restraint matter. The court repeatedly underscored how conservative the government’s presentation was compared to the universe of seized material. That emphasis implicitly warns prosecutors that “overdoing it” could change the Rule 403 balance.
Preservation remains a live appellate hazard. The discussion signals that objections phrased only as “we stipulated” may be deemed insufficiently specific to preserve a distinct complaint about accompanying narration, though the panel did not finally rest on forfeiture.

The likely downstream effect is to make Rule 403 challenges harder where the government uses a small, representative subset and can articulate a clear link to contested knowledge/possession. Conversely, defendants may respond by tailoring stipulations to include additional elements (e.g., knowledge) where possible, though courts may still permit some narrative evidence under Old Chief’s rationale.

4. Complex Concepts Simplified

Stipulation: An agreement between the parties that a fact is true, so it need not be proven. Here, it established that the exhibits depicted actual minors in sexually explicit conduct and commerce elements. It did not establish Ross’s mental state or possession.
Rule 403 balancing: Even relevant evidence can be excluded if its probative value is substantially outweighed by dangers like unfair prejudice or needless cumulativeness. “Unfair prejudice” means persuading the jury to convict for an improper reason (e.g., pure outrage), not merely because the evidence is damaging.
Probative value: How much a piece of evidence tends to make a disputed fact more or less likely. The court deemed the exhibits probative of knowledge (scienter) because the content’s obviousness makes claimed ignorance less plausible.
Scienter / mens rea (“knowingly”): The required guilty mental state. For § 2252A(a)(5)(B), the government must prove the defendant knew he possessed material and knew it contained child pornography.
Abuse of discretion: A deferential appellate standard. The trial judge’s decision stands unless it falls outside the range of reasonable choices.
Plain error vs. harmless error: Plain error applies to unpreserved issues and requires a clear, outcome-relevant mistake that seriously affects the fairness or integrity of proceedings. Harmless error asks whether an error likely affected the verdict.

5. Conclusion

United States v. Ross reaffirms a practical evidentiary principle in CSAM prosecutions: a defendant’s stipulation that certain files meet the legal definition of child pornography does not prevent the government from presenting a limited and representative sample of those files—nor from using brief agent descriptions—when the defense contests possession and knowledge. Guided by Old Chief v. United States and its own precedent in United States v. Ross ("Ross I"), the First Circuit treated restrained publication as legitimate narrative proof of scienter rather than impermissible emotional manipulation. The opinion’s significance lies in its clear message: in Rule 403 terms, the key question is not whether CSAM is prejudicial (it is), but whether the prosecution’s chosen presentation is unfairly prejudicial and needless in light of the issues actually disputed at trial.