On December 9, 2014, at 4:48 p.m., an internal email with the subject line, "Reminder for Tonight and this week: Do Not Advise Protesters That We Are Following Them on Social Media," circulated among dozens of California Highway Patrol commanders. The message read: "A quick reminder ... as you know, our TLO [Terrorism Liaison Officers] officers are actively following multiple leads over social media." The note continued, "this morning, we found posts detailing protesters' interaction with individual officers last night. In the posts, protesters are stating that we (CHP) were claiming to follow them on social media. Please have your personnel refrain from such comments; we want to continue tracking the protesters as much as possible. If they believe we are tracking them, they will go silent."

In recent years, police agencies throughout the United States have scoured social media as part of criminal investigations. But the police are also watching social media to spy on political protesters, especially those they suspect will engage in acts of civil disobedience. During the recent Black Lives Matter protests, local and state police agents monitored protesters on social media and activist websites. Several hundred CHP emails obtained by the Express show that social media is now a key source of intel for the police when monitoring political protests.

But the emails raise serious questions, say civil libertarians and some of the activists whose posts were harvested as intel. How do police monitor social media? Do they store data or track particular people? Are agencies over-reacting and wasting resources? And why are counter-terrorism police involved?

The TLOs tasked by the CHP with monitoring Black Lives Matter protesters on social media are employed by different local agencies and serve as points of contact for matters regarding terrorism. The role was created after 9/11, and the officers communicate through networks coordinated by fusion centers, such as the Northern California Regional Intelligence Center, or NCRIC, which connects police agencies from Monterey County to the Oregon border.

"We don't know as much about the TLO program as we should," said Nadia Kayyali, an activist with the Electronic Frontier Foundation. "We don't know what their standards are, their policies with respect to limits and privacy."

The Twitter user @domainawareness, whose tweets were collected by the police and used as intel, reviewed some of the CHP emails that we obtained. "It's the coordination that's disturbing," said @domainawareness, whom the Express has agreed to not identify. "Everything's totally fusion center-oriented and the information is going very high up."

An email sent on December 12 illustrates how counter-terrorism officials working out of fusion centers helped CHP monitor protesters. At 12:12 p.m. that day, Elijah Owen, a senior intelligence advisor with the California State Threat Assessment Center (Cal STAC) sent CHP officer Michael Berndl a copy of a protest flier calling for a speak-out and march against the CHP the next day. "Just so it's on your folks' radar," wrote Owen. Cal STAC officers appear in other CHP emails as sources of information, or recipients of intel gathered by the Oakland Police Department, Alameda County Sheriff's Office, and other agencies.

"We are not the CHP," Matthew Hopkins the deputy commander of Cal STAC told me. "There are CHP officers in the center, but it's a task force environment. We assess threats. Transnational crime. Terrorism." Hopkins said Cal STAC is a fusion center like NCRIC, except that its main focus is assessing strategic threats to the state of California. Hopkins said he could not comment on any emails sent by his subordinate because he hasn't seen them.

"They've built this big network and they have tremendous resources," said @domainawareness about the involvement of fusion centers in monitoring the Black Lives Matter protests. "But they don't have enough to do, so they're using this to watch political protesters. It's mission creep."

Kayyali added: "There's this mystique around doing surveillance and intel-gathering, and they're not really thinking about the usefulness of what they're doing, and why they're doing it."

Another email circulated among CHP commanders on December 11 included a two-page brief on the department's undercover operations in Oakland and Berkeley in which at least four CHP officers were "[e]mbedded with protesters." According to the brief, these were Terrorism Liaison Officers from CHP's Investigative Services Unit (ISU).

"Up to this point, ISU TLO officers obtained intelligence on protesters through social media regarding dates, times, and locations of planned protests and of intentions to disrupt Bay Area freeways," explained the CHP brief.

The document includes screenshots of tweets, including three from East Bay resident Noura Khouri who took part in the protests. Khouri had tweeted two days before, "Since were dreaming @thehoopoe how about the bay bridge shut down + port shut down + general strike #shutitdown <3." On December 9 Gareth Lacy, a press officer with Caltrans forwarded to CHP commanders a similar tweet composed by @reclaimuc which stated: "may 2, 1992: UC berkeley and berkeley high students occupy bay bridge after acquittal of cops who beat Rodney king." Records show that CHP interpreted social media postings like these as evidence that the Bay Bridge was going to be shut down by protesters.

Acting on this fear, on December 12, CHP Assistant Chief Paul Fontana wrote his commanders requesting special response teams from other divisions. "I would also like to request SWAT," wrote Fontana, referring to the heavily armed special weapons and tactics team.

In an interview, Khouri characterized the reaction of CHP to the protests as extreme and ironic. "These protests initially formed as a direct result of police abuses," said Khouri. "I personally have stopped using Facebook for my political expression because of my deep concern for privacy, and law enforcement using it as a tool of political repression."

The CHP emails show that police were monitoring almost anything related to the Black Lives Matter movement. For example, Maria Dominguez helped organize a "Human Rights Day Vigil" with the nonprofit Ella Baker Center of Oakland on December 10 at the Alameda County Administration Building. "I posted our event on Indybay," said Dominguez in an interview. "We're always cautious of not putting anything online that would raise interest of law enforcement." Dominguez was surprised when she got a phone call from the Alameda County Sheriff's Office.

"When organizers get a call, it is chilling," said Dominguez. "The unsaid thing was, 'warning there's going to be a lot of police there, so if you're planning anything out of line, watch out.'"

Other police agencies flagged Dominguez's event as a threat. In an email with the subject line "RE: Social Media Update," CHP Investigator Timothy Randall emailed half a dozen other officers on December 10, including CHP Chief Avery Browne, and included a screenshot of Dominguez's event posting from Indybay. "Supposed to be just a 'vigil' but it is occurring in Oakland," wrote Randall.

I asked Dominguez why law enforcement might single out her event. "Maybe it's a virtual version of stop and frisk," said Dominguez. "My name is Maria Dominguez. I'm a Latina, and the Ella Baker Center, it's racialized — it's named after a Black woman."

The Oakland Police Department also monitored the Twitter accounts and Facebook postings of Black Lives Matter protesters in December. One "situational awareness" update that OPD sent to the CHP listed a candlelight vigil by Lake Merritt, a Berkeley City Council meeting, and a visit by Mike Brown, Sr. to a San Francisco church as events to monitor.

I called Sergeant Randal Bandino, one of the OPD officers sharing these emails, to ask about how OPD monitors social media. Bandino said he personally isn't involved and can't speak to OPD's practices and policies. But he added, "It's nothing special. What we're looking at is what's open to the public."

Deputy Alameda County Sheriff David Darrin also said he couldn't speak about how his agency monitors social media, referring me instead to the sheriff's official spokesperson. Darrin is also an intelligence officer with the NCRIC fusion center. On December 7, Darrin shared Facebook events advertising upcoming marches "to protest the police riot in Berkeley" with his NCRIC colleague Nicholas Silva. Silva, a CHP officer, forwarded the information on to CHP investigators.

CHP spokesperson Brandie Dressel wrote in an email to me that the CHP has no policies governing the monitoring of social media, but that officers "search for any and all 'open source,' or publicly available, information related our public safety assessments." According to Dressel, the CHP doesn't keep any of this data. As to why Terrorism Liaison Officers were leading the CHP's effort to monitor Black Lives Matter protesters, Dressel wrote, "CHP TLOs can at times be assigned to gather intelligence and provide logistical support for a reasonable and clearly articulated law enforcement purpose."

The emails obtained by the Express from CHP were originally part of a Public Records Act request made by San Francisco resident Michael Petrelis. Petrelis said he asked for the records because he was concerned about CHP's use of less-than-lethal weapons and armed undercover agents. Petrelis also said he is not surprised to see the extensive monitoring of social media by the police. "I come out of Act Up in NYC," said Petrelis. "The cops came to our meetings and they picked up all the lit.

"My experience in organizing is that cops are watching you," he continued. "In the Tech Age, you have to always think the cops are reading this."