Digital Forensics in Child Exploitation Cases: Attorney Resource Guide

Digital Forensics in Child Exploitation Cases

Child sexual abuse material (CSAM) cases present one of the most difficult intersections of law, technology, and constitutional rights. Unlike other criminal matters, the evidence itself is contraband that cannot be freely shared with the defense. Attorneys must work within the constraints of the Adam Walsh Child Protection and Safety Act (AWA), while also understanding how digital forensic artifacts and case law affect whether “knowing possession” can truly be proven. For defense teams, the critical question is not whether files exist, but how they got there, who had control, and whether the government can prove awareness and intent

The Adam Walsh Act and CSAM Evidence Access Limitations

The Adam Walsh Act, enacted in 2006, prohibits duplication of CSAM and requires that evidence remain in government or court custody. Section 504 requires that such materials be made “reasonably available” to the defense, but the term is undefined, and courts have reached different conclusions.   

In United States v. O’Rourke, 470 F. Supp. 2d 1049 (D. Ariz. 2007), the court permitted defense review only at government facilities but stressed that “reasonable availability” required meaningful access and adequate time. In practice, however, defense experts are often restricted to short, heavily monitored sessions in conference rooms with outdated computers. Law enforcement, by contrast, may run unlimited forensic examinations with full toolsets.   

Because of these restrictions, defense experts must treat every review as a one-shot exam, planning carefully in advance to capture logs, metadata, and non-contraband artifacts needed to test the government’s claims. 

How CSAM Investigations Commonly Begin

Most cases begin with referrals to the Cyber Tipline (CTL), operated by the National Center for Missing and Exploited Children (NCMEC). Under 18 U.S.C. § 2258A, electronic service providers (ESPs) must report suspected CSAM. While not required to actively search, many providers, including Google and Microsoft, use PhotoDNA and hash-matching technologies to detect contraband. CyberTips typically include IP addresses, account identifiers, timestamps, filenames and hash values.   

CyberTips are investigative leads, not conclusive evidence. In United States v. Vosburgh, 602 F.3d 512 (3d Cir. 2010), the Third Circuit upheld a conviction based on CyberTip evidence tied to the defendant’s IP address but emphasized the need for corroborating proof.  

Other cases may originate through computer repair shops discovering illicit files, incidental discoveries in unrelated investigations, cryptocurrency tracing, or tips from schools and community members. 

Law Enforcement Forensic Tools and Their Limitations

Law enforcement often relies on modified peer-to-peer (P2P) monitoring tools. ShareazaLE, Torrential Downpour, and RoundUp are common. These programs connect to file-sharing networks such as BitTorrent or eMule and log activity tied to specific IP addresses. Each produces structured log files, including Datawritten.xml, Details.txt, Netstat.txt, and Torrentinfo.txt, which can be requested in discovery without releasing CSAM.   

Courts have recognized the need to scrutinize these tools. In United States v. Chiaradio, 684 F.3d 265 (1st Cir. 2012), the First Circuit emphasized that when the government relies on specialized software, its reliability must be explained through expert testimony.   

Law enforcement also employs Network Investigative Techniques (NITs), which involve taking over illicit websites or servers to capture visitor IP addresses. The FBI’s “Playpen” operation on the The Onion Router (Tor) network is the best-known example. These methods have generated suppression motions, often turning on warrant scope and jurisdiction. 

What a CSAM Defense Digital Forensics Examiner Does

A defense examiner’s role in CSAM prosecutions extends far beyond reviewing government findings. A qualified digital forensics expert may:

1) Replicate Government Methods Using Independent Tools

For computer forensics, common platforms include:

• AccessData FTK

• EnCase

• Magnet AXIOM

• X-Ways Forensics

• Autopsy (open-source)

For mobile forensics, dominant tools include:

• Cellebrite UFED / Physical Analyzer

• Oxygen Forensics Detective

• Magnet AXIOM Mobile

• GrayKey (iOS full file system access and passcode bypass)

Defense experts can expose tool limitations, parsing errors, and gaps created by reliance on one platform.

2) Validate Acquisition and Chain-of-Custody

Key validation areas include:

• imaged bit-for-bit

• hash verification (MD5, SHA-1, SHA-256) were generated and matched

• chain-of-custody documentation was complete

Any deviation opens admissibility challenges.

3) Identify Exculpatory Evidence Beyond Contraband

Defense reviews often expand beyond contraband presence to identify alternative explanations such as:

• malware infections

• unauthorized remote access

• external drive usage

• automatic downloads or cloud sync behaviors

For mobile devices, key artifacts include SQLite databases, usage logs, and app metadata showing content may have been received but never opened.

4) Evaluate Warrant Scope and Fourth Amendment Issues

Overly broad warrants capturing irrelevant data can raise Fourth Amendment challenges.

5) Translate Digital Evidence for Litigation Strategy

Defense experts support attorneys by:

• simplifying complex forensic timelines

• preparing cross-examination angles

• focusing the case on user attribution

In United States v. Ganzer, 922 F.3d 579 (5th Cir. 2019), the court stressed the government must connect contraband to a user—not just a device.

Key Forensic Artifacts in “Knowing Possession” Case Law

Courts repeatedly analyze whether certain digital artifacts prove knowing possession:

• Unallocated Space: In United States v. Flyer, 633 F.3d 911 (9th Cir. 2011), the court overturned a conviction where images were found only in unallocated space, inaccessible without forensic tools.  

• Browser Cache: In United States v. Kuchinski, 469 F.3d 853 (9th Cir. 2006), the court ruled that automatic browser caching did not establish knowing possession absent evidence of awareness.  

• Thumbnails & caching + activity evidence: In United States v. Romm, 455 F.3d 990 (9th Cir. 2006), cached and thumbnail images supported conviction only because the defendant’s browsing activity demonstrated awareness.  

• Knowledge and intent requirement: In United States v. Moreland, 665 F.3d 137 (5th Cir. 2011), the court stressed that the government must prove awareness, not just the technical presence of files.   

• Hash matching authenticity limits: In United States v. Broy, 209 F. Supp. 3d 1045 (C.D. Ill. 2016), the court considered whether hash matches alone could authenticate evidence.  

• Shared devices and attribution gaps: In United States v. Lowe, 516 F.3d 580 (7th Cir. 2008), the court highlighted the difficulty of tying files to a specific user in a multi-user environment.  

Dominion and Control: What “Possession” Actually Requires

Possession in criminal law does not simply mean that a file exists on a computer. It requires both dominion (the power to control the item) and control (the ability to access or use it). Courts have consistently held that a person cannot be convicted of possessing CSAM if the material is present only in areas they cannot reach or if its presence is purely automatic.   

In Kuchinski, the Ninth Circuit explained that without proof a defendant knew about cached files or could access them, conviction would “turn abysmal ignorance into knowledge.” In Flyer, the court emphasized that deleted images in unallocated space did not meet the threshold for possession.   

Dominion and control require proof that the defendant could locate, view, or use the material. Forensic remnants, thumbnails, or automatic copies alone are insufficient. 

User Attribution: The Central Battleground in CSAM Defense

Attribution is often the most decisive issue in CSAM cases. A single IP address or device does not prove who was responsible. The prosecution must show the defendant had dominion and control — that they knew the material was present and had the ability to access or manipulate it.   

Examiners rely on artifacts such as Jump Lists (recently opened files), LNK shortcut files (metadata on deleted targets), Shellbags (folder browsing history), and MRUs (recent documents and URLs). Additional attribution evidence includes browser histories, operating system logs, email/chat account usage, USB connection logs, Wi-Fi connection logs, and cloud sync activity.   

The absence of these artifacts is equally important. If Jump Lists, Shellbags, and MRUs show no evidence that contraband was ever opened, the defense can argue remnants in cache or unallocated space are not possession. This reasoning follows Flyer and Kuchinski.   

Attribution also becomes critical in multi-user settings. A household computer, dorm room, or office machine may have several users. Without evidence tying specific accounts or credentials to the contraband, the case rests on assumptions. In Lowe, the court stressed the government must go further than showing files existing on a shared machine.   

Attribution can also be undermined by open Wi-Fi, malware infections, or remote access, which allow outsiders to introduce files. Defense examiners highlight these factors to show the government cannot prove who actually controlled the content. 

Mobile Forensics: Possession and User Attribution 

Mobile devices introduce unique challenges. Phones are generally tied to a single person through SIM cards, Apple IDs, or Google accounts, but forensic review must still establish dominion and control.   

Possession often depends on whether files were intentionally saved or auto-downloaded. Messaging apps (WhatsApp, Signal, iMessage) and social media platforms (Instagram, TikTok, Facebook) cache images and thumbnails automatically. If files were never opened and the user had no knowledge of them, possession may not be proven.   

Attribution relies on mobile-specific artifacts parsed by tools like Cellebrite UFED/PA, GrayKey, Magnet AXIOM Mobile, and Oxygen Forensics Detective. These include SQLite chat databases, iOS “KnowledgeC” records (tracking app usage), Android “UsageStats,” cloud sync logs (iCloud, Google Photos), account credentials, and biometric unlock logs.   

For example, a UFED extraction may show a file existed on the device, but if KnowledgeC or UsageStats data does not confirm it was opened, attribution weakens. Similarly, group chat pushes can store CSAM on a phone without the user’s consent. Defense experts should emphasize that cached or auto-synced media does not equal knowing possession. 

Emerging Frontier: AI-Generated CSAM and Synthetic Media

Artificial intelligence can fabricate realistic images or videos that never existed. Deepfake services and stripping algorithms now allow creation of synthetic CSAM. While some synthetic media may be protected speech, when minors are depicted, it falls under federal prosecution. Defense attorneys must be prepared to distinguish authentic contraband from synthetic content and challenge detection tools. 

Strategic CSAM Defense Considerations for Attorneys

Defense strategy must be shaped by technical and legal realities. Every exam is a one-time opportunity. Attorneys should move the discussion from “files existed” to whether the government can prove knowledge and control. Automatic system behaviors such as caching, thumbnails, and unallocated remnants should be highlighted as outside user control.   

Alternative explanations — malware, open Wi-Fi, or multi-user systems — must be developed early. By grounding these in case law and forensic artifacts, defense counsel can expose weaknesses in the government’s claims. 

Conclusion

CSAM prosecutions are unlike any other. The Adam Walsh Act restricts access, CyberTips supply investigative leads, and forensic tools provide logs and artifacts. But none of these automatically prove possession. The consistent thread across case law is that possession requires dominion and control.   

By mastering both the technical and legal dimensions — from forensic artifacts to tool reliability — attorneys can challenge assumptions, insist on fairness, and advocate effectively for their clients. 

FAQ 

What does “knowing possession” mean in CSAM cases?

Knowing possession generally requires proof that the defendant was aware of the material and had the ability to access or control it—not just that files existed on a device.

Can cached images or thumbnails prove possession?

Sometimes. Courts often require additional evidence of user awareness or activity. In Kuchinski, automatic caching alone was not enough.

Why is user attribution so important?

Because a device or IP address does not prove who accessed or controlled the files. Attribution requires artifacts tying activity to a specific user account or behavior.

Notable CSAM Digital Forensics Cases

Glossary of Common Terms and Acronyms (Alphabetical Order)

Autopsy: Open-source forensic suite often used for file system and artifact analysis.

AXIOM: Forensic suite from Magnet Forensics, widely used for both computer and mobile evidence analysis.

AWA (Adam Walsh Act): 2006 law governing CSAM evidence access. Section 504 prohibits duplication and requires evidence remain in government or court custody.

Browser Cache: Temporary storage of web content. Files here are often saved automatically by browsers without the user’s knowledge.

Chiaradio (United States v. Chiaradio): Case emphasizing the need for expert explanation when the government relies on specialized investigative software.

CSAM (Child Sexual Abuse Material): Modern legal term replacing “child pornography.” Refers to visual depictions of sexually explicit conduct involving minors.

CTL (CyberTipline): Reporting system managed by NCMEC for suspected CSAM. Receives referrals from electronic service providers (ESPs).

Dominion and Control: Legal standard for possession requiring both awareness of the material and the ability to access or use it.

EnCase: Legacy forensic tool historically used by law enforcement and still widely used in computer forensic investigations.

ESP (Electronic Service Provider): Companies such as Google, Microsoft, Meta, or ISPs. Required by law to report suspected CSAM under federal statutes.

FTK (Forensic Toolkit): Forensic platform known for indexing and large dataset searching, primarily used in computer forensics.

GrayKey: Mobile forensic tool capable of bypassing iOS passcodes and performing full file system extractions.

Hash Value: Cryptographic fingerprint of a file (e.g., MD5, SHA-1, SHA-256) used to prove integrity or match files against known CSAM databases.

Jump List: Windows artifact showing recently opened files or programs, useful in determining whether a file was intentionally accessed.

KnowledgeC (iOS): Apple database that records app usage activity, including launches, screen interaction, and timeline events.

LNK File: Windows shortcut file that stores metadata about another file, often including original path information and timestamps.

Lowe (United States v. Lowe): Case highlighting attribution challenges in multi-user environments and the limits of proving possession through device ownership alone.

MRU (Most Recently Used): Lists tracking recently opened documents, files, or URLs, often used to support user attribution.

NCMEC (National Center for Missing and Exploited Children): Nonprofit organization that operates the CyberTipline and forwards reports to law enforcement.

NIT (Network Investigative Technique): Law enforcement technique involving control or compromise of systems to identify users (e.g., collecting visitor IP addresses in Tor investigations such as “Playpen”).

P2P (Peer-to-Peer): File-sharing networks such as BitTorrent or eMule that are frequently monitored in CSAM investigations.

Romm (United States v. Romm): Case allowing cached and thumbnail images to support conviction where user browsing activity demonstrated awareness.

Shellbags: Windows artifacts that record folder browsing history and view settings, often used to show directory navigation and access.

SQLite Database: Lightweight database format commonly used by apps (e.g., WhatsApp, iMessage) to store messages, media references, and activity logs.

UFED (Universal Forensic Extraction Device): Mobile forensic tool from Cellebrite used to extract and analyze data from phones and tablets.

Unallocated Space: Portion of a storage device marked as available for new data but which may still contain remnants of deleted files; not accessible through normal user activity.

UsageStats (Android): System log tracking app usage on Android devices, often used for attribution and timeline reconstruction.

Vosburgh (United States v. Vosburgh): Case upholding conviction tied to CyberTip evidence while emphasizing the need for corroboration beyond an IP address alone.