What defenses have courts accepted in cases about online-only viewing of CSAM?
Executive summary
Federal and circuit courts have accepted several defenses in cases involving online-only viewing of CSAM, chiefly that a private third party’s automated or manual screening qualifies as a “private search” insulating later government review from the Fourth Amendment, and challenges to government expansion beyond the scope of that private search—an approach that produced a notable Ninth Circuit ruling finding a Fourth Amendment violation in United States v. Wilson (discussed in law reviews and reports) [1] [2]. Legislative activity (e.g., the STOP CSAM Act of 2025) and state statutes are changing incentives for platform screening and reporting, raising unresolved questions about when provider screening becomes state action [3] [1].
1. Private-search doctrine has been the go-to defense — and courts have sometimes accepted it
Defense teams and some courts have relied on the private-search doctrine to argue that when a service provider’s tools (like hashing or automated filters) flag files, any subsequent government review is not a new “search” under the Fourth Amendment. Courts and commentators cite cases where the government’s review was treated as an extension of a private actor’s earlier screening because the provider had already identified apparent contraband using reliable hashing or matching tools [2] [1]. Library of Congress analysis describes this line of reasoning and notes lower courts that have invoked the high reliability of hashing and analogies to earlier Supreme Court precedent to justify treating provider screening as private [1].
2. The Ninth Circuit pushed back — viewing by agents can be a constitutional search
Not all courts accept the private-search cover blanket. The Ninth Circuit in United States v. Wilson reversed a district court and held that a government agent’s viewing of email attachments flagged by Google violated the Fourth Amendment; the panel concluded the government exceeded what Google’s private search accomplished and found gaps in the government’s claims about the screening tool’s accuracy [2]. The Ninth Circuit’s focus on whether the government “expanded” the private search produced a circuit split that commentators and Congress have flagged as unsettled law [1] [2].
3. “Virtual certainty” and scope-of-search doctrines produce alternative defenses and counter-arguments
Some district courts invoked doctrines like “virtual certainty” — the idea that a follow-up inspection could reveal nothing about noncontraband items — to justify warrantless review where contraband is essentially certain; others rejected that, demanding more proof of screening accuracy before excusing a warrant [2]. Scholars note these divergent applications and emphasize that courts differ on how much reliability and specificity in provider screening is enough to avoid Fourth Amendment constraints [2] [1].
4. Statutory reporting regimes and new laws complicate the state-action analysis
Congressional reporting obligations (e.g., the PROTECT-era reporting to NCMEC) and new bills like the STOP CSAM Act of 2025 change incentives for private providers to scan and report CSAM and create pressure points for courts deciding whether provider behavior counts as state action; Library of Congress analysis warns that inducements or statutory procedures could make provider searches look like government searches under state-action doctrine [1] [3]. The STOP CSAM Act would also expand reporting requirements and civil liability, altering the factual environment judges must consider [3] [4].
5. Criminal-defense strategy also includes evidentiary and possession arguments
Beyond Fourth Amendment labels, defense attorneys routinely challenge the government’s proof of possession and chain-of-custody, arguing that files on a device do not automatically prove knowing possession and demanding inventories, limited disclosure, or protective orders for CSAM shown to defendants — issues discussed in practitioner guides and legislative analyses of court rules for handling CSAM evidence [5] [6]. Some courts have balanced defendant access to evidence against victim privacy by restricting copying but allowing controlled viewing [6].
6. Unresolved questions: accuracy, copying, and AI-generated material
Sources show courts and commentators wrestling with how accurate screening tools must be for the private-search defense to succeed and whether viewing identical hashed files elsewhere equals viewing the flagged files themselves [1] [2]. Separate litigation over AI-generated or “virtual” CSAM raises First Amendment and possession questions, with courts sometimes distinguishing real-child CSAM from virtual content — a complexity that feeds back into how courts treat automated detection and government review [7] [8].
Limitations and final context: available sources document major cases, doctrinal lines, legislative proposals, and practitioner strategies but do not offer an exhaustive catalog of every defense accepted in every jurisdiction; many outcomes depend on detailed factual showings about how screening works and whether government agents exceeded private searches [2] [1]. Courts will continue to split on whether provider screening is effectively a government search as Congress advances new reporting and liability rules that may tilt the state-action inquiry [1] [3].