In the mid-1960s, the MPD launched a domestic intelligence unit to spy not just on activists, but also on teachers’ meetings, a college black student union and labor organizers. That included Martin Luther King Jr., who came to Memphis in the spring of 1968 to stand in solidarity with underpaid and mistreated black city sanitation workers.

The police surveillance wasn’t conducted just with wiretaps and long lenses, but with snitches planted within local organizations, including spies planted by then-Mayor Henry Loeb, an anti-union segregationist, among sanitation workers who wanted to join a union.

In the iconic photo taken just moments after a gunman shot King on the Lorraine Motel balcony, several people are seen pointing in the direction from which the bullet came. Crouched over King’s body is a man holding a towel to the gaping wound on King’s face. The man, rarely identified in photos, is Marrell “Mac” McCollough, a Memphis cop who was assigned to infiltrate a militant activist group hated by Memphis police. There’s no evidence he was involved with King’s assassination.

Some, including members of King’s family, have long speculated that the assassination was not the work of a lone gunman but orchestrated by federal law enforcement agencies (the FBI famously monitored and harassed King). Both a U.S. House committee independent review in 1979 and a Department of Justice review in 2000 found no basis for this. Still, in 2002, the National Civil Rights Museum, which sits where the motel was, added to its permanent exhibits “Lingering Questions,” which contains hundreds of pieces of evidence, including the bullet plucked from King’s body. One of the questions (that the exhibit does not definitively answer): “Was the Memphis Police Department part of the conspiracy?”

In 1976, the ACLU of Tennessee sued the city, alleging it had violated residents’ First Amendment rights by maintaining records that “contained unverified information and gossip which related exclusively to the exercise of lawful and peaceful activities,” and, according to the complaint, “served no lawful or valid law enforcement purpose.”

A judge agreed and in 1978 signed the Kendrick consent decree, the first such decree in the country, which barred law enforcement from surveilling protesters for political purposes.