Abstract network diagram illustrating a Carpenter IP address BitTorrent investigation.

When defense attorneys see a BitTorrent CSAM investigation that spans months or years, they often ask: does Carpenter v. United States apply here?

The answer, so far, has been no. Courts consistently distinguish public peer-to-peer file sharing from the historical cell-site location information (CSLI) that Carpenter protected. Still, the question matters because it sits at the intersection of digital privacy doctrine and large-scale Internet Crimes Against Children (ICAC) monitoring.

This post explains Carpenter’s core holding, why defendants try to analogize it to long-term P2P surveillance, and why courts have rejected that analogy. It also identifies the factual patterns that might change the analysis in future cases.

The Carpenter decision as a digital privacy precedent

Carpenter v. United States, decided in 2018, held that when the government acquires historical cell-site location information from a wireless carrier, that acquisition is a search under the Fourth Amendment and generally requires a warrant supported by probable cause [1].

The Court emphasized the “depth, breadth, and comprehensive reach” of CSLI and how it enables “near perfect surveillance” of a person’s movements over time. In doing so, Carpenter carved out an exception to the traditional third-party doctrine, which had held that if a suspect voluntarily shared information with a company, they lacked a reasonable expectation of privacy in those records.

Carpenter limited that logic for highly revealing, long-term location data. Because of this, commentators describe Carpenter as a digital privacy precedent that invites courts to reexamine how the Fourth Amendment applies to modern digital surveillance techniques, including IP-based investigations and large-scale monitoring of online activity [2].

For digital investigators, Carpenter raises an important question: when does metadata, including IP addresses and session logs, become so comprehensive and revealing that it triggers Carpenter’s warrant requirement? That question sits at the center of the emerging IP-based forensics standard.

How CSAM BitTorrent investigations work (law enforcement side)

In the CSAM context, law enforcement uses peer-to-peer tools to monitor BitTorrent swarms for known contraband. Torrential Downpour, for example, is a law enforcement-only Child Protection System (CPS) program that searches the BitTorrent network for hash values of files already identified as CSAM and attempts to download those files directly from a single IP address [3].

A simplified law enforcement workflow in a CSAM BitTorrent case looks like this:

  1. The investigator loads one or more target torrent hashes—corresponding to known CSAM—into Torrential Downpour or a similar CPS tool.
  2. The program searches public BitTorrent swarms for peers advertising those hashes and logs the IP addresses and ports that appear to offer the files.
  3. The program attempts a Torrential Downpour single-source download from one IP address at a time and records the communication logs (timestamps, infohash, file paths, and other metadata).
  4. Once a successful download completes and the file hashes match known CSAM, the investigator issues a subpoena to the ISP to identify the subscriber assigned that IP address at the relevant time.
  5. Based on the downloaded material, the logs, and the subscriber information, law enforcement applies for a search warrant and executes it at the physical location associated with the subscriber account.
  6. Forensic examiners then image seized devices and correlate artifacts (BitTorrent clients, logs, and CSAM files) with the network evidence.

At each stage, the investigator generates technical artifacts: Torrential Downpour logs, ISP subscriber records, and device-level forensic data. Those artifacts are the core materials that a defense forensic expert will later review.

Importantly, in BitTorrent CSAM cases, only law enforcement personnel run Torrential Downpour or similar CPS tools against live swarms. Defense experts do not run parallel CSAM searches on the live network; they analyze how the original investigation was conducted, using the data and logs that already exist.

What defense forensic experts do (after the fact)

Defense forensic experts step in after the law enforcement investigation and warrant execution. Their role is fundamentally different from that of a law enforcement analyst:

  • They do not initiate BitTorrent CSAM investigations or connect to swarms.
  • They do not run Torrential Downpour against live targets.
  • Instead, they examine the digital record of what law enforcement already did.

Typical tasks for a defense forensic expert include:

  • Reviewing Torrential Downpour logs to verify which IP address was targeted, which files were requested, and what the tool actually downloaded. (For a practical guide to the highest-value run artifacts, see Datawritten.xml and downloadstatus.xml.)
  • Confirming that the file hashes downloaded by law enforcement match the hashes on the seized devices, or identifying gaps where they do not match.
  • Examining the BitTorrent client configuration and logs on seized devices to determine whether the device could have been the source Torrential Downpour connected to.
  • Reviewing ISP records, including dynamic lease information and any network address translation (NAT) or carrier-grade NAT details that may weaken the link between IP address and account holder.
  • Comparing the technical record against the warrant affidavit to see whether the affidavit accurately described the technology and evidence.

Defense experts also help counsel assess whether a Carpenter-based argument is plausible. For example, does the investigation involve a one-time connection to a publicly shared file, or does it involve long-term, large-scale tracking of IP addresses across many swarms and time periods? That distinction is central to the emerging peer-to-peer evidentiary shift.

How courts have applied Carpenter to BitTorrent CSAM cases

Defendants in several CSAM BitTorrent cases have tried to use the Carpenter decision to suppress evidence obtained through Torrential Downpour and similar tools. So far, courts have remained unconvinced that downloading files or metadata from a publicly shared BitTorrent client falls within Carpenter’s protection.

United States v. Hoeffener (Eighth Circuit)

In United States v. Hoeffener, the Eighth Circuit considered a challenge to Torrential Downpour in a BitTorrent CSAM case [3]. The court held that the defendant had no legitimate expectation of privacy in files he made available to the public through a P2P file-sharing network, even after Carpenter.

The panel emphasized that Torrential Downpour only downloaded files that the defendant’s BitTorrent client had already offered publicly, and that the software did not access non-public areas of the computer.

This reasoning fits a line of cases that treat P2P file sharing as functionally equivalent to placing contraband on a public website for anyone to download. Under that view, no search occurs when law enforcement downloads what any member of the public could have downloaded.

Youngman v. State (Florida Second DCA)

In Youngman v. State, the Florida Second District Court of Appeal addressed Torrential Downpour in a state CSAM case [4]. The court described Torrential Downpour as a Child Protection System tool “available only to law enforcement” that automates the process of searching for hash values of known CSAM on BitTorrent. The opinion emphasized that the software “merely automates the aggregation of public information,” a task that investigators could have carried out manually by connecting to the swarm and downloading the same files.

Youngman reinforces the idea that, as long as law enforcement only accesses files that have been voluntarily shared with the public, no new Fourth Amendment search occurs, even when an automated tool performs the work.

United States v. Carme (District of Massachusetts)

In United States v. Carme, the defendant argued that the use of Torrential Downpour and subsequent seizure of his devices violated Carpenter because the investigation allegedly built a detailed profile of his digital activity [5]. The district court rejected this argument. It concluded that the Carpenter decision did not apply where law enforcement downloaded files the defendant had made available on a public P2P network and then used a standard subpoena and warrant process to identify and search his devices.

The Carme court also noted that a more elaborate explanation of how Carpenter might apply to aggregated third-party data in the P2P context would require different facts—specifically, evidence that the government engaged in long-term, comprehensive monitoring that resembled the “near perfect surveillance” Carpenter addressed.

United States v. Ewing (Eleventh Circuit)

More recently, in United States v. Ewing, the Eleventh Circuit addressed a Carpenter-based challenge to a BitTorrent CSAM investigation [6]. The court held that there is no reasonable expectation of privacy in files made publicly available through BitTorrent, and law enforcement’s download did not violate the Fourth Amendment. The court distinguished Carpenter by emphasizing that the defendant had voluntarily exposed the files to the public through the P2P network.

Why courts distinguish public P2P exposure from historical CSLI

The consistent theme across these cases is the voluntary exposure doctrine. Courts distinguish public P2P exposure from historical CSLI in several ways:

Voluntary public sharing vs. passive location tracking

In Carpenter, the government obtained location data that the defendant did not voluntarily share with the public. The defendant used a cell phone for communication, but the location tracking was a byproduct of that use, not something the defendant intended to expose.

In BitTorrent cases, by contrast, courts view the defendant as having voluntarily placed files on a public network where anyone can download them. That voluntary act distinguishes the case from the passive tracking in Carpenter.

Publicly shared files vs. private location records

Carpenter involved private records held by a third party (the wireless carrier). The defendant had no control over who could access those records, but they were not publicly accessible.

In BitTorrent cases, the files are publicly accessible to anyone who connects to the swarm. Courts treat that public accessibility as a key distinction.

One-time downloads vs. comprehensive surveillance

Most BitTorrent CSAM cases involve discrete downloads over a limited time period. Carpenter, by contrast, involved “near perfect surveillance” over an extended period that revealed a comprehensive picture of the defendant’s movements.

Courts have been reluctant to extend Carpenter to investigations that involve downloading publicly shared files, even when those downloads occur over time, because the files remain publicly accessible throughout.

Watch list: what factual patterns might change the analysis

While current case law favors law enforcement, certain factual patterns might make a Carpenter-based argument more plausible in future cases. Defense attorneys should watch for these patterns:

Dragnet monitoring across many swarms

If an investigation involves monitoring the same IP address across hundreds or thousands of different torrents over an extended period, that begins to resemble the “depth, breadth, and comprehensive reach” that Carpenter addressed. The more the investigation looks like longitudinal tracking of a person’s digital activity, the stronger a Carpenter argument may become.

Long-term tracking of specific IPs

If law enforcement maintains a database tracking specific IP addresses across multiple investigations and time periods, that could trigger Carpenter concerns. The question would be whether that tracking creates a “mosaic” of digital activity that reveals more than any single download.

Nonpublic data collection

If the investigation involves accessing data that was not publicly shared—for example, accessing a directory that was not part of the shared torrent, or obtaining information through methods that bypass normal protocol participation—that could distinguish the case from the typical public exposure scenario.

ISP subscriber records in the context of mass monitoring

The status of ISP subscriber records in the context of large-scale ICAC monitoring is less clear. If law enforcement conducts extensive BitTorrent swarm monitoring and then repeatedly subpoenas ISPs for subscriber information linked to that monitoring, the question becomes more complex.

Whether the ISP account-holder information linked to that long-term, large-scale data collection should require a search warrant may not be fully tested in current case law.

Commentators at organizations like NACDL’s Fourth Amendment Center have argued that Carpenter’s logic may apply to certain forms of aggregated third-party data that reveal a person’s “digital travels, personal curiosities, and online associations” over time [2].

This is where the peer-to-peer evidentiary shift intersects with the Fourth Amendment. The difference is between a snapshot of public activity (Hoeffener/Ewing) and a surveillance mosaic of a user’s life (Carpenter). A one-time download from a public swarm looks very different from years of continuous monitoring of the same IP address across thousands of torrents, followed by repeated subpoenas for subscriber information.

Practical motion tips: don’t oversell; anchor to specific facts and logs

If you are considering a Carpenter-based suppression motion, here are practical tips:

Anchor to specific facts, not abstract theory

Do not argue that all BitTorrent investigations violate Carpenter. Instead, identify the specific facts that make your case different:

  • How many torrents were monitored?
  • Over what time period?
  • Was the same IP address tracked across multiple investigations?
  • Were ISP subscriber records obtained repeatedly?
  • Does the investigation reveal a comprehensive picture of the defendant’s digital activity?

Use the logs to build your timeline

Torrential Downpour logs can help you reconstruct the investigation timeline. Use them to show:

  • When monitoring began and ended.
  • How many different torrents were involved.
  • Whether the same IP address appeared in multiple swarms.
  • Whether subscriber information was obtained multiple times.

Distinguish your case from Hoeffener and Ewing

Acknowledge the prevailing case law, but explain why your facts are different. If you have evidence of long-term, comprehensive monitoring, emphasize that. If you have evidence of nonpublic data collection, emphasize that.

Consider the ISP subscriber records angle separately

Even if the BitTorrent downloads themselves do not trigger Carpenter, the repeated acquisition of ISP subscriber records in the context of mass monitoring might. Consider arguing that aspect separately, especially if your case involves multiple subpoenas over an extended period.

Conclusion

The Carpenter decision reshaped the Fourth Amendment analysis for certain kinds of third-party digital data, especially historical location records. In CSAM BitTorrent investigations, however, courts have repeatedly held that defendants lack a reasonable expectation of privacy in files they share publicly on P2P networks.

Cases such as United States v. Hoeffener, Youngman v. State, United States v. Carme, and United States v. Ewing show that the Carpenter ruling has not persuaded courts to suppress evidence obtained when law enforcement uses Torrential Downpour to download publicly offered files and then subpoenas ISPs for subscriber information.

At the same time, the digital privacy precedent set by Carpenter v. United States continues to influence how courts and commentators think about large-scale, long-term monitoring of online activity.

In the ICAC context, the question of whether extensive BitTorrent swarm monitoring combined with ISP account-holder lookups should require a warrant under Carpenter has not been fully tested [7].

Law enforcement analysts who run CSAM BitTorrent investigations must document their work carefully and respect current limits. Defense forensic experts must scrutinize those investigations after the fact, translating complex technical records into arguments that fit within an evolving IP-based forensics standard.

If you are a criminal defense attorney handling a CSAM BitTorrent case, or a defense forensic expert reviewing a Torrential Downpour investigation, you do not need to navigate these technical and legal issues alone. Lucid Truth Technologies can help reconstruct the investigation, analyze the evidence, and prepare clear, courtroom-ready explanations that account for both the Carpenter decision and current case law on peer-to-peer evidence.

Contact us using the LTT contact form: Contact.

Continue reading

This article is for informational purposes and does not provide legal advice. Every case turns on specific facts and controlling law in your jurisdiction. Work with qualified counsel and, where appropriate, a qualified expert.

References

[1] Supreme Court of the United States, Carpenter v. United States, 138 S. Ct. 2206, 2018. [Online]. Available: https://www.supremecourt.gov/opinions/17pdf/16-402_h315.pdf

[2] M. Price and B. Wolf, “Building on Carpenter: Six New Fourth Amendment Challenges Every Defense Lawyer Should Consider,” National Association of Criminal Defense Lawyers (NACDL), 2018. [Online]. Available: https://www.nacdl.org/Content/Building-on-Carpenter-Six-New-Fourth-Amendment-Cha

[3] United States Court of Appeals for the Eighth Circuit, United States v. Hoeffener, 950 F.3d 1037, 2020. [Online]. Available: https://law.justia.com/cases/federal/appellate-courts/ca8/19-1192/19-1192-2020-02-24.html

[4] District Court of Appeal of Florida, Second District, Youngman v. State, 342 So. 3d 770, 2022. [Online]. Available: https://caselaw.findlaw.com/court/fl-district-court-of-appeal/2178390.html

[5] United States District Court for the District of Massachusetts, United States v. Carme, No. 1:19-cr-10073, 2020. [Online]. Available: https://www.govinfo.gov/content/pkg/USCOURTS-mad-1_19-cr-10073/pdf/USCOURTS-mad-1_19-cr-10073-0.pdf

[6] United States Court of Appeals for the Eleventh Circuit, United States v. Ewing, No. 24-11308, 2025. [Online]. Available: https://law.justia.com/cases/federal/appellate-courts/ca11/24-11308/24-11308-2025-06-23.html

[7] K. G. Hartman, “Carpenter Decision and IP-based Investigations in Digital Forensic Practice,” Lucid Truth Technologies, 2025. [Online]. Available: https://lucidtruthtechnologies.com/carpenter-decision-and-ip-based-investigations/