Baltimore Aerial Surveillance: What Canada Can Take From the Recent Decision

On June 24, 2021, in Leaders of a Beautiful Struggle v Baltimore Police Department,[1] the US Court of Appeals for the Fourth Circuit On Rehearing En Blanc decided that Baltimore’s use of an aerial surveillance pilot program violated the Fourth Amendment.[2] The court remanded the matter for further proceedings consistent with the opinion. In this article, I describe the technology that was used in Baltimore, review what transpired leading up to the decision, explain the decision, and suggest insights that Canada may take from the decision.

The Program

In March, 2020, the Baltimore Police Department (BPD) decided to proceed with an Aerial Investigation Research (AIR) pilot program (Program) beginning on May 1, 2020. For up to 180 days, one or more aircrafts operated approximately 40 hours per week and collected imagery of over 90 percent of Baltimore City. The technology’s resolution was one pixel per person, making individuals and vehicles appear as single dots that could be tracked from a crime scene. The purpose of the Program was to support the investigation of serious offenses such as murder, non-fatal shootings, armed robberies, and car-jackings; the captured data was provided to both prosecution and defense attorneys in specific cases.

The Program used experimental aerial investigation research technology and analytics to assist the BPD with investigating crimes, and was designed to determine whether AIR was effective for accomplishing the project’s goals. The goals included: increasing the solvability of crimes; improving clearance rates; improving police community relations; and deterring criminal activity. To accomplish its goals, the BPD engaged a private company, Persistent Surveillance Solutions, to fly three planes over Baltimore during daytime hours. Also, the Program was funded by private philanthropists.

Despite the technology’s resolution, the captured imagery was integrated with other BPD systems in order to assist in investigations; some of these technologies included ground-based cameras (CCTV cameras) and licence plate readers (to identify vehicles).

Notably, the Program contained data retention policies and privacy protection measures. In particular, there were target data imagery retention times of 45 days and several privacy measures, some of which included limits on the crimes and activities that could be analyzed; the use of AIR imagery and data; and the locations, individuals, and vehicles that could be analyzed.

Following the introduction of the Program, several civil liberties groups opposed the surveillance, calling it the “spy plane”.

Events Leading Up to the Decision

In response to the BPD’s plan to use the Program, the plaintiffs sued the BPD and the police Commissioner, arguing that the Program was unconstitutional because it violated the Fourth Amendment. The plaintiffs filed a motion for a temporary restraining order and a preliminary injunction, but the district court denied this request (the plaintiffs appealed this decision the same day). The court later decided that the plaintiffs’ Fourth Amendment claim was unlikely to succeed on the merits—the plaintiffs filed a petition for rehearing en banc.

The Program came to an end, and a decision was made to not continue with the Program. Most of the data was deleted over a two-week period in order to minimize retained data. The data that was retained, 14.2 percent of the captured imagery data, was thought to be the minimum amount necessary to support reports and the prosecution and defence teams in the 200 cases aided by the Program, 150 of which were open investigations.

In response to the termination of the Program, the defendants filed a motion to dismiss for mootness. The en banc hearing took place shortly thereafter.

Decision of the US Court of Appeals for the Fourth Circuit—On Rehearing En Banc

Writing for the majority, Gregory, Chief Judge, discussed the defendants’ attempt to dismiss the plaintiffs’ claims on the ground of mootness and the plaintiffs’ Fourth Amendment claim and request for preliminary relief.

1. Mootness

With respect to the defendants’ motion to dismiss the appeal on the ground of mootness, the court explained that a case became moot when the issues that were presented were no longer live, or the parties lacked a legally cognizable interest in the outcome. That is, it had to be impossible for a court to grant an effectual relief to the prevailing party. A case was not moot if the parties had a concrete interest, however small, in the outcome of the litigation.

In this case, the defendants argued that the Program had ended, the data collection had stopped, no new tracking analysis was taking place, and the agreement with the contractor had been terminated—the plaintiffs’ request for preliminary relief was now moot.

But the majority of the court disagreed and stated that the appeal presented a live controversy since the plaintiffs had requested that the BPD stop operating the Program and accessing any stored images created during the lawsuit. Gregory, Chief Judge, stated: “While the planes have stopped flying, the fruits of the AIR program persist”. Because the BPD stored the images and reports of about 200 criminal cases and was free to access them at any time, the plaintiffs had a concrete interest in the outcome and it was possible for the court to grant them effectual relief. And there were several reasons why the BPD might access the tracked movements and underlying images that it had, such as confirming or discrediting new information that arose. It also did not matter that a large portion of the data was deleted:

But 14.2 percent of all the data collected—millions of photographs documenting thousands of hours of public movements over six months—is a significant quantity of information

To that end, the court denied the defendants’ motion to dismiss the appeal.

2. Decision

The court explained that to obtain a preliminary injunction, plaintiffs had to establish the following: i) they were likely to succeed on the merits; ii) they were likely to suffer irreparable harm absent preliminary relief; iii) the balance of the equities favored relief; and iv) the relief was in the public interest. The court also clarified that the Fourth Amendment safeguarded the right of the people to be secure against unreasonable searches and seizures, absent a warrant. Additionally, the court referred to a landmark Supreme Court case, Carpenter v United States,[3] and noted that the purpose of the Fourth Amendment was to safeguard privacy and security of individuals against arbitrary invasions by governmental officials. In Carpenter, the court decided on the ability to chronicle a person’s past movements through a record of cell phone signals; the court found that the personal location information at issue was deeply revealing in nature—given its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the government’s acquisition of the cell-site records constituted a search under the Fourth Amendment.

In this case, the plaintiffs argued that the Program violated the principles in Carpenter, and the court agreed. In fact, it disagreed with the district court’s interpretation of the facts, namely that the Program had limited location tracking abilities because it only depicted individuals as miniscule dots moving about a city landscape, the planes did not fly at night and could not capture images in inclement weather, and gaps in the data would prohibit the tracking of individuals over the course of multiple days. Confirming that the district court misapprehended the evidence, Gregory, Chief Judge, stated:

From that premise, it believed the AIR program could not expose the “privacies of life.”

More specifically, the court confirmed that Carpenter identified a reasonable expectation of privacy in the whole of a person’s physical movements, and also the idea that government access to this information went against that expectation. Essentially, there was a difference between short-term tracking of public movements (something that law enforcement would do before the digital age) and prolonged tracking that could reveal intimate details through habits and patterns (something that invaded the reasonable expectation of privacy that individuals had in the whole of their movements, requiring a warrant).

The court had no trouble finding that Carpenter applied squarely to this case since the Program tracked every movement of every person who was outside in Baltimore—the data was a detailed, encyclopedic record of where everyone came and went within the city during daylight hours. The court suggested that the AIR data was similar to attaching an ankle monitor to every person in the city. The nature of the Program was such that, although not perfect tracking, it yielded a wealth of detail and enabled deductions about what a person did or did not do. Gregory, Chief Judge, stated:

Therefore, because the AIR program opens “an intimate window” into a person’s associations and activities, it violates the reasonable expectation of privacy individuals have in the whole of their movements

And the defendants’ efforts to limit data collection to daylight hours and reduce resolution did not make the Program equivalent to traditional short-term surveillance—the information that was captured was sufficient for law enforcement to deduce the people behind the pixels; they could use any number of context clues to distinguish individuals and deduce identity. Some of these clues stemmed from city cameras, licence plate readers, and gunshot detectors.

Accordingly, the court found that, because the Program enabled police to deduce from the whole of individuals’ movements, accessing its data constituted a search, and its warrantless operation violated the Fourth Amendment. As a result, the court held that the plaintiffs’ Fourth Amendment challenge was likely to succeed on the merits. Also, the court briefly concluded that the remaining part of the test was met in favour of preliminary relief.

The court added that mass surveillance touched everyone, but its effect was strongest on disadvantaged communities by their poverty, race, religion, ethnicity, and immigration status as they were the least empowered to object. The court stressed that this was why it was important to stay rooted on constitutional principles; it was important to respect innovation in policing, yet simultaneously respect the role of the warrant.

Therefore, the court reversed the denial of plaintiffs’ motion for a preliminary injunction and remanded the matter for further proceedings consistent with this opinion.

What Can Canada Take from This Development?

While this case took place in the United States and Canada has not had a program like the BPD’s Program that would have triggered claims under section 8 of the Canadian Charter of Rights and Freedoms,[4] there are several insights that can be taken regarding the nature of aerial surveillance and surveillance technology used by police.

As noted above, the court stressed that the district court did not entirely appreciate the nature of the aerial surveillance and downplayed its impact. It is critical to fully understand the technology’s potential to expose the privacies of life, especially when the captured data is combined with other technologies to produce contextual clues into a person’s associations and activities. Simply put, this case sent a strong message that it is not acceptable to violate the reasonable expectation of privacy that individuals have in the whole of their movements.

The Program used real-time, prolonged surveillance of everyone in Baltimore, and the court equated this to all Baltimoreans being forced to wear ankle monitors. There is no question that continuous surveillance comes with serious dangers; this panoptic surveillance causes chilling effects and causes individuals to modify their behaviour through self censorship.[5] To prevent the abuse of surveillance power, reasonable suspicion needs to be established and the least intrusive means of obtaining the information need to be utilized. This is why it is so important to obtain a warrant with these sorts of searches.

The court also emphasized the importance of respecting innovative policing, but simultaneously remaining rooted on constitutional principles. This meant that it was not possible to use newer technologies to open an intimate window and enable deductions into individuals’ private lives, all of which had a stronger impact on disadvantaged groups.

Interestingly, this case involved private-public partnerships between the BPD and private contractors and funders. In the Office of the Privacy Commissioner of Canada’s Remarks at the IAPP Canada Privacy Symposium 2021, the Privacy Commissioner of Canada recognized the increased role of public-private partnerships and contracting relationships, and noted that these relationships involving digital technologies had the potential of creating additional complexities and risks. It appears that there are some grey areas with public-private partnerships, especially in the context of policing—and further clarity is needed on how to respect the privacy of individuals equally in both spheres.

– Christina Catenacci, BA, LLB, LLM, PhD


[1] Leaders of a Beautiful Struggle v Baltimore Police Department, No 20-1495 (4th Cir 2021) [Leaders of a Beautiful Struggle v Baltimore Police Department].

[2] US Const amend IV [Fourth Amendment].

[3] Carpenter v United States, 585 US ___ (2018) [Carpenter].

[4] Canadian Charter of Rights and Freedoms, s 7, Part 1 of the Constitution Act, 1982, being Schedule B to the Canada Act 1982 (UK),1982, c 11 [Charter]. Section 8 is similar to the Fourth Amendment in that it states that everyone has the right to be secure against unreasonable search or seizure.

[5] Christina Catenacci, “Privacy and Surveillance in the Workplace: Closing the Electronic Surveillance Gap” (2020) at 26–83, 265–286, online (pdf): Scholarship@Western <> [Electronic Thesis and Dissertation Repository: 7117].

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