{"id":64420,"date":"2026-07-09T18:53:48","date_gmt":"2026-07-09T23:53:48","guid":{"rendered":"https:\/\/fourthamendment.com\/?p=64420"},"modified":"2026-07-09T18:54:24","modified_gmt":"2026-07-09T23:54:24","slug":"ca11-google-computers-csam-hash-value-search-and-match-was-private-search-noting-circuit-split","status":"publish","type":"post","link":"http:\/\/fourthamendment.com\/?p=64420","title":{"rendered":"CA11: Google computer’s CSAM hash value search and match was private search, noting circuit split"},"content":{"rendered":"\n

A Google computer\u2019s hash value match of a file passing through Google to a CSAM image then forwarded on to NCMEC was a private search. The court agrees with the Fifth and Sixth Circuits holding that the private search doctrine applies, and noting: \u201cThe Second, Fourth, and Ninth Circuits have held, to the contrary, that a hash-value match cannot constitute a valid private search.\u201d United States v. Brillhart<\/a>, 24-13226 (11th Cir. July 9, 2026):<\/p>\n\n\n\n\n\n\n\n

\n

As our descriptions indicate, to this point, most private-search cases (at least in this circuit) have involved a flesh-and-blood individual\u2019s review of a disputed piece of evidence. The central question here is whether Google\u2019s digital hash-value matching protocol should be treated the same way for private-search purposes. Recall, first, the nature of the hash value: A hash value is a string of characters that together constitute a file\u2019s unique \u201cdigital signature or fingerprint,\u201d such that \u201cif two files ha[ve] the same hash value, they\u2019re the same file[.]\u201d Tr. of Mot. to Suppress Hr\u2019g at 20.<\/p>\n\n\n\n

Recall, next, Google\u2019s particular hash-matching protocol: After an individual Google employee confirms through human review that a particular file depicts child pornography, that file\u2019s hash value is added to a company database along with a corresponding \u201cindustry classification\u201d describing the file\u2019s contents. Id. at 101, 105. If, thereafter, an automated process reveals that another file\u2019s hash value matches one in the database, Google concludes\u2014without further human review\u2014that it\u2019s the same file and forwards it along with its classification to NCMEC. Id. at 121\u201322, 124.<\/p>\n\n\n\n

Our sister circuits are split over whether hash matching constitutes a valid private search. The Fifth and Sixth Circuits have held that it does and, therefore, that a subsequent search by law
enforcement of the same images falls within the scope of the hash-match search, and thus of the private-search doctrine. See United States v. Reddick, 900 F.3d 636 (5th Cir. 2018); United States v. Miller, 982 F.3d 412 (6th Cir. 2020). In so holding, both courts emphasized the \u201cnear-perfect accuracy\u201d of hash-value matching\u2014which, they say, ensures that law enforcement \u201clearn[s] nothing \u2026 that it had not already learned from the private search.\u201d Reddick, 900 F.3d at 640; Miller, 982 F.3d at 418.<\/p>\n\n\n\n

The Second, Fourth, and Ninth Circuits have held, to the contrary, that a hash-value match cannot constitute a valid private search. See United States v. Maher, 120 F.4th 297, 314 (2d Cir. 2024); United States v. Lowers, 170 F.4th 134, 156 (4th Cir. 2026); United States v. Wilson, 13 F.4th 961, 971 (9th Cir. 2021). Although their approaches differ at the margins, all three courts have conceived of a digital file as akin to a \u201ccontainer[]\u201d or a \u201csealed manila envelope\u201d whose precise contents can\u2019t really be known until a human opens it. Lowers, 170 F.4th at 149 & n.9; Maher, 120 F.4th at 317 (analogizing digital files found on two separate email accounts to two different sealed containers in the physical world); Wilson, 13 F.4th at 973, 977 n.13 (emphasizing that the image files were \u201cunopened\u201d). They have also emphasized that because Fourth Amendment rights are \u201cpersonal,\u201d a private search that uses information gleaned from a file that was once in the possession of a third party can\u2019t defeat the suspect\u2019s privacy interests, even in the very same file. Lowers, 170 F.4th at 153\u201354; Maher, 120 F.4th at 319; Wilson, 13 F.4th at 975.<\/p>\n\n\n\n

We agree with the Fifth and Sixth Circuits, and thus hold that Google\u2019s application of its hash-matching protocol to Brillhart\u2019s file qualifies as a valid private search. Through hash matching, Google simply used a computer to save one flesh-and-blood individual the trouble of having to confirm what another (or perhaps even the same) flesh-and-blood individual had already concluded. It\u2019s worth noting at the outset that, at least as Google employs it, hash-value matching doesn\u2019t replace human review entirely. Rather, at step one, so to speak, an individual Google employee reviews a file, determines that it depicts child pornography, assigns it a hash value and classification, and enters it into the company\u2019s database. See Tr. of Mot. to Suppress Hr\u2019g at 76, 101. It is only at step two that the automated hash match occurs: A computer compares a new file\u2019s hash value against those in the database known to depict child pornography and, if (but only if) there\u2019s a match, reports the new file as child pornography. Id. at 124.<\/p>\n\n\n\n

Under Supreme Court precedent, the controlling question is whether there is \u201cvirtual certainty\u201d that law enforcement will find \u201cnothing else of significance\u201d in its own review that hadn\u2019t already been revealed by the private search\u2014here, that the digital file depicts child pornography. Jacobsen, 466 U.S. at 119. We are satisfied that the search at issue here satisfies that test.<\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"

A Google computer\u2019s hash value match of a file passing through Google to a CSAM image then forwarded on to NCMEC was a private search. The court agrees with the Fifth and Sixth Circuits holding that the private search doctrine … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,43],"tags":[],"class_list":["post-64420","post","type-post","status-publish","format-standard","hentry","category-computer-searches","category-private-search"],"_links":{"self":[{"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/posts\/64420","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=64420"}],"version-history":[{"count":2,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/posts\/64420\/revisions"}],"predecessor-version":[{"id":64422,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=\/wp\/v2\/posts\/64420\/revisions\/64422"}],"wp:attachment":[{"href":"http:\/\/fourthamendment.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=64420"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=64420"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/fourthamendment.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=64420"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}