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Fourth Amendment

 “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."  
- U.S. Const. amend. IV. 

NACDL seeks to ensure that the Fourth Amendment remains a vibrant protection against encroachments on the privacy of the individual through litigation and public advocacy. The Fourth Amendment is the appropriate starting point for assessing the limits on government intrusion into one's privacy, and its protections must continue to thrive in the digital age. The Fourth Amendment and its guarantees should not turn on the medium used to transmit private information, nor on how the information is stored. NACDL strives to guarantee that evidence obtained in violation of the Fourth Amendment is excluded in a court of law.

Fourth Amendment Center


4ac logo 

NACDL's Fourth Amendment Center offers direct assistance to defense lawyers handling cases involving new technologies and tactics that may infringe on privacy rights of Americans.

The Center's staff is available to help members of the defense bar in bringing new Fourth Amendment challenges, providing a range of support: from training and resources to expert consultation and direct litigation, all free of charge. Launched in April 2018, the Fourth Amendment Center seeks to build a robust legal infrastructure to challenge outdated legal doctrines that undermine privacy rights in the digital age. To this end, the Center is now available provide litigation assistance in cases raising new Fourth Amendment concerns, including:

  • Searches & seizures of personal data held by "third-party" service providers (the "third-party doctrine");
  • Overbroad searches & seizures of electronic devices or online accounts;
  • Electronic location tracking, including cell site simulators ("Stingrays");
  • Government hacking and use of "network investigative techniques";
  • New law enforcement technologies: predictive policing, facial recognition and biometric identification, and drone/aerial surveillance.

Defense lawyers with cases involving any of these issues are encouraged to contact NACDL's Fourth Amendment Center.

Fourth Amendment Center Tech Advisory Board

The Tech Advisory Board is made up of defense attorneys, academics, and technologists who help ensure that Fourth Amendment case law evolves to keep pace with emerging technologies. Learn more about the Board here.

The Center is available to provide consultations and litigation resources as well as direct assistance in support of a defendant's Fourth Amendment claims.

Specifically, the Center may assist in motion practice, preparation for suppression hearings, as well as appellate strategy, brief writing, and oral argument. The Center also provides group trainings for defense lawyers around the country and upon request.

To request assistance or additional information, contact 4AC@nacdl.org. 

Compelled Decryption Primer

If a device is locked or encrypted, can law enforcement compel a suspect to unlock or decrypt it? Read NACDL's primer on this emerging issue.

Can the government force someone to decrypt a digital device? Encryption is as omnipresent as computers, tablets and smartphones, yet the Supreme Court has not ruled on the constitutional implications of compelled decryption orders. The Fourth Amendment Center has published a Compelled Decryption Primer that outlines the state of the law and offers guidance for lawyers litigating this important emerging issue. The realities of modern technology require a rethinking of old doctrines to adequately safeguard constitutional rights into the future. Using this primer, attorneys can educate themselves on the basics of compelled decryption and come equipped with arguments and cases when confronting a decryption order.

Read "Split Over Compelled Decryption Deepens With Massachusetts Case" by Michael Price and Zach Simonetti, featured in Just Security.

"It has been almost a decade since Apple first offered encryption on iPhones, but the legal fight over compelled decryption remains a pitched battle. A recent volley saw the Massachusetts Supreme Judicial Court double down on the wrong side of recurring litigation over when, if ever, the government can force someone to decrypt a digital device that has been seized pursuant to a valid search warrant. As encryption winds its way into the U.S. Supreme Court’s vocabulary, defense lawyers and advocates should pay careful attention to these developments – and be prepared to confront them in court."

Combatting the Surveillance State in Criminal Proceedings

This two-day CLE conference discussed the government's use of technologically advanced investigative techniques in criminal cases, and the issues raised by those techniques under the Fourth Amendment and other federal law.

Advanced technologies are revolutionizing how the government investigates, charges and prosecutes criminal cases—and defense attorneys must keep pace. Even small police departments can purchase powerful surveillance technologies, and internet companies collect vast troves of data on virtually everyone. This CLE was co-sponsored by NACDL and the Berkeley Center for Law and Technology (BCLT), and held at International House, the University of California - Berkeley from November 29 to 30, 2018.


Digital Device Searches - Searching Computers, Phones, and Even Your Home AppliancesEsha Bhandari, Staff Attorney, ACLU Speech, Privacy, and Technology Project; Catherine Crump, Director, Samuelson Law, Technology & Public Policy Clinic at U.C. Berkeley School of Law; Michael Price, Senior Litigation Counsel, NACDL Fourth Amendment Center

Recognizing and Challenging Facial Recognition Technology in Criminal Cases Clare Garvie, Associate, Center on Privacy & Technology at Georgetown University Law Center; Kaitlin Jackson, Attorney, Bronx Defenders; Joshua Kroll, Postdoctoral Research Scholar, UC Berkeley School of Information 

Flash Talk: Protecting Your Communications From Big BrotherMatt Mitchell, Director of Digital Safety & Privacy for Tactical Tech

Who’s Reading Your Clients’ Posts? Social Media Monitoring in Criminal CasesMatt Cagle, Staff Attorney, ACLU of Northern California; Hanni Fakhoury, Assistant Federal Public Defender, Federal Public Defender's Office (N.D. Cal.)

Parallel Construction – Defending Your Client When the Government Launders EvidenceAshley Gorski, Staff Attorney, ACLU National Security Project; Brian Pori, Assistant Federal Public Defender, Federal Public Defender’s Office (D. N.M.); Sarah St. Vincent, Researcher and Advocate, Human Rights Watch U.S. Program

Defending Cases in Body Camera Jurisdictions – Deborah Katz Levi, Assistant Public Defender, MD Office of the Public Defender; Jumana Musa, Director, Fourth Amendment Center, NACDL; Harlan Yu, Executive Director, Upturn

Flash Talk: Using Big Data as a Shield– Tracking Police MisconductCynthia Conti-Cook, Staff Attorney, Special Litigation Unit, Legal Aid Society of New York

Flash Talk: Biometrics Beyond Facial RecognitionJennifer Lynch, Senior Staff Attorney, Electronic Frontier Foundation

Algorithms and Criminal Justice – Litigating the Black BoxStephanie Lacambra, Criminal Defense Staff Attorney, Electronic Frontier Foundation; Rashida Richardson, Director of Policy Research, AI Now Institute; Andrea Roth, Assistant Professor of Law, U.C. Berkeley School of Law

Challenging Government Hacking in Criminal CasesColin Fieman, Senior Litigator, Federal Public Defender’s Office (W.D. Wash.); Jonathan Mayer, Assistant Professor, Princeton University; Riana Pfefferkorn, Associate Director of Surveillance and Cybersecurity, Center for Internet and Society at Stanford Law School

Flash Talk: Recent Changes to How Law Enforcement Gets Digital Evidence: GDPR & the Cloud ActGreg Nojeim, Senior Counsel & Director of Freedom, Security and Technology Project, Center for Democracy & Technology

Flash Talk: What I Wish I Knew When I Had Your JobHon. Kate Menendez, Magistrate Judge, District of Minnesota

Where We Go from Here: The Third-Party Doctrine and Location Tracking After CarpenterMegan Graham, Clinical Teaching Fellow, Samuelson Clinic for Law, Technology & Public Policy; Hon. Stephen Smith, Director of Fourth Amendment & Open Courts, Center for Internet and Society at Stanford Law School; Nathan Freed Wessler, Staff Attorney, ACLU Speech, Privacy, and Technology Project

The Future of the Fourth Amendment

"Building on Carpenter: Six New Fourth Amendment Challenges Every Defense Lawyer Should Consider" by Michael Price, Senior Litigation Counsel, and Bill Wolf, member of NACDL's Board of Directors and NACDL's Fourth Amendment Advocacy Committee.

"The implications of the Supreme Court's decision in Carpenter v. United States are just now coming into view as lower courts begin to apply Carpenter's lessons to other forms of modern surveillance. [...] This article offers a snapshot of some current investigative techniques that may be ripe for constitutional challenges in a post-Carpenter world." 

Read "Concealing Evidence: 'Parallel Construction,' Federal Investigations, and the Constitution," written by Natasha Babazadeh and published in the Fall 2018 issue of the Virginia Journal of Law and Technology.

"Federal law enforcement agencies are increasingly relying on “parallel construction" to pursue criminal cases against U.S. persons. Parallel construction is the process of building a separate — and parallel — evidentiary basis for a criminal investigation. The process is undertaken to conceal the original source of evidence, which may have been obtained unlawfully. Clandestinely used for decades, this process raises serious constitutional questions."

The June 2018 issue of The Champion featured "Carpenter v. United States and the Future Fourth Amendment" by Michael Price, Senior Litigation Counsel.

"The Supreme Court's recent opinion in Carpenter v. United States has set a course for rethinking Fourth Amendment rights in the digital age. It is the third bright star in the last seven years, marking a welcome and long overdue departure from the so-called 'third-party doctrine' that has limited privacy rights for the last four decades. In a 5-4 decision, the Court ruled that police must usually get a warrant to access historical 'cell site location information' (CSLI) — geographic data held by a cellphone service provider about where a device has connected to its network. It is a major win for privacy rights and it shines the way forward for future Fourth Amendment challenges: digital is different. The question becomes, different how? And how far might Carpenter extend?"

Facial Recognition Webinar

"Face-Off: Recognizing and Challenging the Use of Facial Recognition Technology"

On September 18, NACDL held a free webinar about the practices, risks, and limitations of emerging facial recognition technology. With an increasing number of police departments across the country turning to unregulated, untested, and flawed facial recognition technology to identify suspects, it is vital defenders understand the technology, its limitations, and how to challenge its use in their cases. This webinar explored these issues with the Georgetown Law Center of Privacy and Technology's Clare Garvie, Bronx Defender's Kaitlin Jackson, and computer scientist Joshua Kroll. This webinar was supported by Grant No. 2013-MU-BX-K014 awarded by the Bureau of Justice Assistance. 

Surveillance Self Defense

The Fourth Amendment is being redefined in the digital age. Surveillance programs and technologies that were ostensibly created and implemented to combat terrorism are being used in every aspect of the criminal justice system. NACDL is producing a series of primers to introduce different surveillance programs and techniques to defense lawyers and provide strategies and resources to combat them in cases. This is an ongoing project and will be updated periodically.

Location Privacy after Carpenter

On July 2, 2018, the Center on Privacy and Technology at Georgetown Law and the Fourth Amendment Center at the National Association of Criminal Defense Lawyers hosted a forum discussing location and cell phone privacy after the Supreme Court ruling in Carpenter v. United States.

The Supreme Court held, in a 5-4 decision, that law enforcement agencies are required to obtain a warrant when accessing historic cell site location information. Featuring the insight of privacy experts and seasoned litigators, the discussion explored both the broad implications of the landmark ruling and the practical ramifications on future litigation. The program included Nathan Freed Wessler, who argued the case for Carpenter, Laura Donahue a Fourth Amendment expert and professor at Georgetown Law, and Maryland defense attorney Jason Downs along with other privacy experts, attorneys and technologists.

Location Privacy after Carpenter, Part 1: Big Picture Implications of the Carpenter decision – Featuring Dr. Sibren Isaacman, cellular network data expert, Assistant Professor at Loyola University Maryland; Nathan Freed Wessler, ACLU Attorney for petitioner Timothy Ivory Carpenter; Professor Laura Donohue, Fourth Amendment expert, Georgetown University Law Center; Professor Stephanie Pell, location privacy expert and former Hill staffer, West Point's Cyber Institute. Moderated by Alvaro Bedoya, Executive Director of the Center of Privacy and Technology at Georgetown Law.

Location Privacy after Carpenter Part 2: Practical Implications of the Carpenter decision – Featuring Jason Downs, criminal litigation expert, Downs Collins; Todd Hesel, appellate criminal prosecutor, Maryland Office of the Attorney General; Matt Mitchell, digital safety and privacy expert, Tactical Technology Collective and Crypto Harlem. Moderated by Jumana Musa, Director of the Fourth Amendment Center at the National Association of Criminal Defense Lawyers.

Parallel Construction Webinar

“Unknown Unknowns: How to Expose the Government's Evidence Laundering"

On May 23, 2018, NACDL held a free webinar about the practice of government evidence laundering, known as “parallel construction." When the U.S. government launders the origin of evidence obtained in criminal cases, it is able to obscure secret surveillance technology or potentially unconstitutional investigative methods from the accused in criminal cases. The webinar featured Brian Pori, a federal public defender from New Mexico with extensive experience leading trainings on government evidence laundering, and Sarah St. Vincent, the author of Human Rights Watch's comprehensive investigative report “Dark Side: Secret Origins of Evidence in US Criminal Cases."

Protecting Your Digital Devices at the Border

This primer aims to educate attorneys about the implications of CBP's claimed powers and offer strategies that will help them comply with their ethical obligations and responsibilities to their clients when entering the U.S. Along with the primer, NACDL compiled a resource of district court cases that deal with the border search exception and digital devices, with special attention paid to the influence of Riley v. California.  

Read "Protecting Your Digital Devices at the Border: A Criminal Defense Lawyer's Primer" here and find the companion case list here

CBP updates directive on border searches of digital devices 

On January 4, 2018, Customs and Border Protection (CBP) released a directive on the border searches of digital devices that made significant changes to the practices that NACDL detailed in “Protecting Your Digital Devices at the Border: A Criminal Defense Lawyer's Primer." The directive includes specific procedures to protect attorney-client privilege and work product doctrine, as well as a dangerous new provision that asserts travels have an "obligation" to provide CBP with their device passwords. You can learn more about the directive from Esha Bandari at the ACLU, the Deeplinks blog at the Electronic Frontier Foundation, and Edward Hasbrouck's two-part analysis of the password provision.

Digital Device Search Webinar

"Privileged Means Privileged: Keeping the Government Out of Your Digital Devices at the Border"

U.S. Customs and Border Protection (CBP) searches the digital devices of people at border crossings and at ports of entry without a warrant and without suspicion. NACDL members are uniquely exposed to abuse in this context: digital devices store materials and information subject to the attorney-client privilege and attorney work-product doctrine, as well as information on overseas clients and witnesses, and other extremely sensitive materials that could be covered by Rule 1.6 of the Model Rules of Professional Responsibility.

The webinar was presented by Esha Bhandari, a staff attorney with the ACLU Speech, Privacy, and Technology Project, where she focuses on litigation and advocacy relating to online speech, academic freedom, privacy rights, and the impact of big data. She is counsel for the plaintiffs in Alasaad v. Duke, a challenge to the government's practice of conducting warrantless searches of electronic devices at the border. Esha was previously an Equal Justice Works Fellow with the ACLU Immigrants' Rights Project, where she was involved in litigating cases concerning a right to counsel in immigration proceedings, detainer policies, and discriminatory state and local laws. She has also been a staff attorney at the Center for Reproductive Rights, where she worked on two trials challenging a Texas law limiting women's access to reproductive health care. Esha is a graduate of McGill University, the Columbia University Graduate School of Journalism, and Columbia Law School, and served as a law clerk to the Hon. Amalya L. Kearse of the U.S. Court of Appeals for the Second Circuit.

Challenging Government Hacking in Criminal Cases

NACDL published a guide on challenging evidence seized by government-installed computer malware, authored by the American Civil Liberties Union with input from NACDL and the Electronic Frontier Foundation.

The guide, “Challenging Government Hacking in Criminal Cases," examines recent court decisions on the government's use of malware in the context of Fourth Amendment protections from unreasonable searches. NACDL hosted a webinar on the guide featuring the expertise of Colin Fieman, an Assistant Federal Public Defender and lead counsel in the first “Operation Pacifier" cases, and Paul Ohm, a law professor and specialist in information privacy, computer crime law, intellectual property, and criminal procedure.

Watch our new webinar "Defending Government Hacking Cases" here

Body Camera Webinar

"Policing Body Cameras - Shaping Policies and Defending Cases in Body Camera Jurisdictions"

This report outlines NACDL's position on the introduction and use of body cameras by law enforcement. This webinar walks through the recommendations and talks about how to negotiate stronger body camera policies in your jurisdiction, the technical aspects of body cameras, and strategies and tactics for defending clients in body camera jurisdictions. 

Encryption Webinar

"Keep It Confidential: Protecting Your Privileged Client Communications with Encryption" 

Defense lawyers regularly use phone calls, texts, and emails to communicate with clients, investigators, witnesses and others associated with their cases. Many of these communications are privileged, yet government surveillance programs can capture and store them. This webinar explored how this happens, and how defense lawyers can keep their communications out of government hands.

During the first part of the webinar, Jack Gillum, reporter on The Associated Press's Washington investigations team, addressed his experience with encrypting communications and why he and others in his industry have made the switch to these encrypted platforms. Neema Singh Guliani, Legislative Counsel at the American Civil Liberties Union, then laid out the different surveillance programs and technologies that may be intercepting your privileged communications. 

During the second part of the webinar, Harlo Holmes, Digital Security Trainer with the Freedom of the Press Foundation, walked through some basic ways to encrypt phone calls, texts, and email communications. 

News Of Interest

" Judge Urged to Block Warrantless Tech Searches at Border," by Zack Huffman, Courthouse News Service, July 18, 2019.

"Oakland Police Conducted An Illegal Search And Then Lied About It. But They May Be Spared From Discipline.," by Darwin BondGraham, The Appeal, July 17, 2019.

"Opinion: What We’ve Learned From Our Privacy Project (So Far)," by Susan Fowler, New York Times, July 16, 2019.

"Disneyland Makes Surveillance Palatable—and Profitable," by Austin Carr, Bloomberg, July 15, 2019.

"Facial Recognition Tech Is Growing Stronger, Thanks to Your Face," by Cade Metz, The New York Times, July 13, 2019.

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