The Ninth Circuit Court of Appeals heard oral arguments last week in Sanchez v. the Los Angeles Department of Transportation, a case about whether riders of electric ride-share scooters have a reasonable expectation of privacy over the location and routes of their scooters. The argument lays bare the tension many courts are experiencing in applying Carpenter v. United States to circumstances beyond cell phones.
Electric ride-share scooters have grown in number across the United States and around the world. This mode of transportation has taken off in particular in Los Angeles, with more than 36,000 scooters registered. The companies which own the scooters collect detailed data about scooter locations and routes taken, and this data is at the center of a case currently pending in the Ninth Circuit. In September 2018, the Los Angeles City Council passed an ordinance that, among other things, required scooter operating companies to hand over historical vehicle location and trip data to the Los Angeles Department of Transportation (“LADOT”) as part of a program called the Mobility Data Specification (“MDS”). The data is anonymized and unlinked to any individual rider, but it is accurate to a “few dozen feet.” Plaintiffs Justin Sanchez and Eric Alejo, who ride electric scooters to commute, shop, and socialize, sued the City, alleging that MDS violates the Fourth Amendment in light of Carpenter v. United States.
In Carpenter, the Supreme Court held that an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through cell-site location data (“CSLI”) collected by third parties. The nature of cell phones and our close relationships with them are such that when the government tracks the location of a cell phone it “achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.” Tracking someone’s cell phone location reveals an intimate window into someone’s life, including associations and relationships to others. Given this intimate revelation, the fact that the Government obtained the information from a third party did not overcome Carpenter’s Fourth Amendment claim. In the years since Carpenter, federal and state courts have cited the cases nearly one thousand times.
The Oral Argument
On March 8, 2022, the Ninth Circuit heard argument in Sanchez v. LADOT. Sanchez appealed the district court’s motion to dismiss the case. Mohammad Tajsar from the ACLU of Southern California, represented Sanchez. Tajsar argued that the city had no justification for warrantless dragnet surveillance of “maximally precise” location data on every single ride of every single passenger in the city. Plaintiff argued that this case falls squarely within Carpenter, particularly noting that the method of surveillance here is “easy, cheap, and efficient,” language the Carpenter Court used to describe the CSLI.
Early in the argument, Judge Hurwitz asked whether scooters are different from cellphones for purposes of applying Carpenter, given that plaintiffs enter into transactions requiring them to disclose their location to a third party during the transaction. Judge Hurwitz also pointed out that the surveillance in Carpenter was continuous, whereas here the data covers discrete trips.
Tasjar replied that Carpenter makes clear that “knowing sharing” of data is not the end all be all, and that these discrete trips can, as in Carpenter, reveal sensitive information about the riders. For instance, the MDS data reveals someone’s commute from home to work and everywhere else they have been on a ride-share scooter, like a political meeting, support group, or planned parenthood clinic. Judge Rosenthal’s questions clarified that the plaintiff is not troubled by the collection of this data from the scooter operator, but rather the compelled transfer of that data to LADOT.
The City, meanwhile, argued that the data collected has no relation to an individual until the data is analyzed, and therefore there is no constitutional issue present. Jonathan H. Eisenman, representing the city, conceded that there would be a Fourth Amendment violation if LADOT collected the identity of each rider in a dragnet fashion. However, it is the case that even anonymized data sets with the granularity present in MDS can be used to identify people, particularly where location data is collected at a high frequency, as it is here.
Judge Hurwitz probed whether privacy protections were built into the regulation authorizing the data collection. The City replied that there is none in the rule itself, but that LADOT has a policy of not sharing the data. Judge Hurwitz was unsatisfied by the response, asking for a codified privacy rule. “It’s my policy not to yell at my law clerks,” Judge Hurwitz said, “until I get angry and then sometimes I forget my policy.”
Asked whether the LAPD can call LADOT and ask for the location data, the City answered that it doesn’t make much of a difference if LAPD could otherwise just get the information from the scooter company. This prompted each judge on the panel to interrupt with the same point: it makes a difference. The difference is that in order to get the data from the scooter company, the police would have to show either probable cause or specific and articulable facts that the data would benefit an ongoing investigation.
The district court below wrote that unlike the cellphone data at issue in Carpenter, “riding a one-time rental scooter is not indispensable to modern life.” Yet plaintiffs alleged that these ride-share scooters are necessary for many, especially in car-centric Los Angeles, to commute to work and connect to other forms of mass transit. Judge Wardlaw picked up on issue, pointing out that Sanchez does not have a car and that many people do find the scooters necessary.
Tasjar ended his rebuttal by emphasizing the stakes of this case. “Recent history has taught us that the entire architecture of our digital lives as we live them today is mediated by third parties that collect all kinds of information about us,” he explained. “We are just beginning to understand just how invasive and revelatory all that information is.” This case highlights the issues courts are grappling with as they apply Carpenter to different facts and novel technologies. As different circuits diverge in their interpretation of Carpenter in light of their own precedents, the Supreme Court may soon have to weigh in yet again.
 Mark Puente and Laura J. Nelson, As Scooters Flood Los Angeles, The Number of Tickets Written to Riders Is Soaring, Los Angeles Times, Aug. 23, 2019, https://www.latimes.com/california/story/2019-08-22/electric-scooters-sidewalk-helmet-los-angeles-bird-lyft-lime-jump-tickets-lapd.
 Sanchez v. LADOT, Case No. 21-55285 (9th Cir. 2022) (pending).
 Sanchez v. LADOT, 2021 WL 1220690, *1 (C.D. Cal. 2021).
 Carpenter v. United States, 138 S. Ct. 2206 (2018).
 Id. at 2217.
 Id. at 2218.
 Id. at 2217.
 Id. at 2200.
 Matthew Tokson, The Aftermath of Carpenter: An Empirical Study of Fourth Amendment Law, 2018—2021, 135 Harv. L. Rev. __ (2022) (forthcoming).
 Sanchez v. LADOT, supra note 2.
 Oral Argument at 4:30, Sanchez v. LADOT, Case No. 21-55285 (9th Cir. 2022) (pending).
 Id. at 6:40.
 Appellant’s Opening Brief at 9, Sanchez v. LADOT, Case No. 21-55285 (9th Cir. 2022) (pending).
 Oral Argument, supra note 12 at 8:40.
 Id. at 23:20.
 Dániel Kondor et al. Towards Matching User Mobility Traces in Large-Scale Datasets, 6 IEEE Transactions on Big Data,
 Oral Argument at 30:45.
 Id. at 29:24.
 See, e.g., the Stored Communications Act, 18 U.S.C. § 2701 et seq., and the Electronic Communications Privacy Act, 18 U.S.C. § 2510 et seq. (applying to stored data and distinguishing between content and non-content information).
 Sandchez v. LADOT, supra note 3 at *4.
 Opening Brief, supra note 14, at 1.
 Oral Argument, at 39:20.
 Oral Argument at 45:30, Sanchez v. LADOT, Case No. 21-55285 (9th Cir. 2022) (pending).