How have courts treated thumbnail and cache evidence in CSAM convictions since Romm and Moreland?

1. Romm set a permissive starting point — but it was fact‑specific

The Ninth Circuit in Romm upheld convictions where automatic cache copies and thumbnails were part of the proof because forensic analysis showed the defendant had enlarged several thumbnail images and otherwise engaged in browsing behavior that demonstrated control and awareness — the court treated thumbnails as probative only within that factual constellation, not as a blanket rule that automatic caching equals knowing possession ^{[1] [2]}.

2. Moreland and other circuits pushed back: knowledge and access matter

Subsequent opinions emphasized that “mere” automatic caching or thumbnail creation does not transform passive remnants into criminal possession; the Fifth Circuit in Moreland and other courts required additional proof that a defendant knew of and could access or re‑access the images, drawing a line between innocuous browser artifacts and the mens rea element of possession offenses ^[2].

3. Case law since Romm: a circuit split in texture, not principle

Post‑Romm decisions reveal a functional—if not always formally labeled—split: the Ninth (and some courts like in Tosti and Miller) have been prepared to treat enlarged thumbnails or technician‑viewed images as nonsearches or admissible evidence in context, while other circuits demand corroborating activity or proof of control before permitting convictions based solely on cached thumbnails or deleted fragments ^{[3] [2]}. Courts have stressed that treating automatic copies as possession without proof of awareness would “turn abysmal ignorance into knowledge,” a criticism reflected in decisions cited in reporting and legal commentary ^[2].

4. Forensics and attribution drive the evidentiary calculus

Across circuits, practitioners and judges focus on forensic indicators of dominion and control — evidence the user could copy, print, delete, or otherwise access files — as decisive, because thumbnails and cache entries alone often cannot be reliably tied to human intent or exclusive possession; commentators and forensic guides likewise flag attribution as “often the most decisive issue” in CSAM prosecutions ^{[2] [4]}.

5. Fourth Amendment and private‑screening complications

The role of provider screening and algorithmic flagging has complicated suppression and admissibility fights: cases like Wilson illustrate judicial concern about relying on private detections absent proof the underlying algorithms reliably distinguish contraband from innocuous content, and some courts have treated provider or technician viewing of thumbnails as either outside the Fourth Amendment’s search rubric or as permissible only where accuracy and prior viewing are established ^{[3] [5]}.

6. Scholarly critique and policy stakes

Law review and advocacy scholarship warn that treating thumbnails and cache remnants as dispositive risks converting automatic technical artifacts into criminal proof absent human intent, urging clearer standards and noting the prosecutorial benefits of expansive readings; at the same time, victim‑protection and prosecutorial sources emphasize that modern investigative workflows — CyberTip reports, hash‑matching, and forensic tools — are essential to finding and stopping abuse, creating tension between privacy and enforcement goals ^{[4] [2] [6]}.

7. Practical takeaway for courts and litigants

The controlling lesson in the post‑Romm/Moreland era is doctrinally consistent if factually cautious: thumbnails and cached files are admissible and can support convictions when corroborated by other proof of awareness, access, or control (enlargement, repeated access, associated user activity); absent those indicia, several courts refuse to let automatic browser artifacts alone establish the knowing possession required by federal statutes ^{[1] [2]}.