In its ongoing legal battle with Calvary Chapel, Santa Clara County used mobile phone data to map concentrations of congregants gathering on the church’s Hillsdale Avenue grounds and conducted multiple stealthy inspections in late 2020 and early 2021 that experts say raise major civil liberties questions.
The use of third-party phone data — a technique known as “geofencing” — and the numerous visits by enforcement officers reveal the lengths to which a county known for its strict COVID response was willing to go in order to prove that the church was breaking the rules.
The county is currently seeking nearly $3 million in public health fines from Calvary, a nondenominational Christian church with 3,000 congregants. Whether or not the church will fork over the money depends on the outcomes of state and federal cases that have been winding their way through the courts for nearly three years.
“It is unconscionable how much time and money this county has spent surveilling and targeting this church when they should be focused on rebuilding the community,” said Mariah Gondeiro, an attorney for Calvary Chapel.
In one striking example of the surveillance efforts, inspection officers with the county’s COVID-19 Business Compliance Unit parked a car at a neighboring church’s lot to observe the Calvary Chapel worshippers' behavior on four separate occasions in August and September of 2020.
Officials at the Central Church of Christ, separated from Calvary by a chain link fence, asked the inspection officers to stop using its premises as a surveillance post that October, minister Alexander Tullis said. An official of the church initially permitted the county’s use of their property, but its leaders eventually pushed back on the idea, Tullis said. The county complied.
Altogether, the county’s inspectors made 44 visits at or near Calvary Chapel between August 2020 and January 2021 at a cost of $219 an hour, repeatedly observing congregants gathering maskless and in large crowds as COVID numbers peaked — and before a vaccine was widely available, court records show.
The church, led by pastor Mike McClure, has not denied that it broke the county’s COVID rules but has pushed back on the county fines, claiming that he and his congregation had the right to gather during the pandemic.
County Counsel James Williams, whose office is pursuing the fines against Calvary, defended the use of the mobile phone data, which is anonymized, and the observation efforts by inspection officers.
He said it’s likely the first time the surveillance technology has been used by the county in litigation but contended that Calvary Chapel was a unique public health hazard during the pandemic to which the county was compelled to respond. He confirmed the county has not tracked the cellphones of individuals at the church.
As for the inspectors’ actions, Williams said it is not unusual for government enforcement officials to utilize such techniques to ensure businesses are in compliance — such as a tobacco shop suspected of selling cigarettes to minors.
The court documents and their contents were first reported this week by independent journalist David Zweig.
Mike Katz-Lacabe, director of research at the San Leandro-based Center for Human Rights and Privacy, said the use of geofencing in this particular case raises major civil liberties questions. Though the mobile phone data may be anonymized, Katz-Lacabe said that it is possible that the feature could be circumvented to allow tracking of individuals.
“There are all kinds of concerns with geofencing when you talk about your First Amendment rights like freedom of expression or freedom of religion,” he said. “You could conceivably use it to see who goes to a mosque — or discriminate against certain religious groups or minorities.”
In one example cited by Katz-Lacabe, anti-abortion groups in 2016 used such technology to send ads to women who were at abortion clinics, urging them to reconsider their choices.
In the case of Calvary Chapel, Katz-Lacabe said the use of geofencing is juxtaposed with concerns around public health. “That is a balancing act that we as a society continue to struggle with,” he said.
A federal court filing submitted in November shows the county utilized data from the Denver-based company SafeGraph to prove, from an analytics standpoint, that Calvary Chapel’s services from March 2020 to 2021 were uniquely large compared to other public and private spaces throughout the county.
Geofencing uses aggregate mobile phone data points to show patterns of movement. The technology is used by law enforcement and more recently during the pandemic by public health agencies to understand the impact of social distancing on populations. The SafeGraph data relies on the company’s vast tranche of 47 million mobile phone devices across the country that opt-in to location tracking. In the case of Calvary Chapel, the county hired Stanford Law Professor Daniel Ho at a rate of $800 per hour to pore over data that specifically captured movement within the boundaries of the church’s property.
“Given available knowledge about the spread of COVID-19 in indoor spaces with unmasked activity … there were strong reasons to believe that Calvary posed an unusually high risk,” he wrote.
In a statement, Ho said he helped the county as an expert witness, “exclusively to analyze preexisting, aggregate mobility data to determine whether visit patterns for Calvary Chapel in 2020-2021 were outliers relative to other facilities.”
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