A former Rohnert Park police sergeant has broken years of silence in federal court, testifying that he and a fellow officer impersonated federal agents, pulled over unsuspecting drivers along Highway 101, and stole their cash and cannabis.

Brendan “Jacy” Tatum — who led the city’s now-defunct drug interdiction team before pleading guilty to federal charges in 2021 — took the witness stand Tuesday in the criminal trial of Joseph Huffaker, another former Rohnert Park cop who was once under Tatum’s command.

The trial, unfolding this week in U.S. District Court in San Francisco, centers on a conspiracy that prosecutors say began even after California legalized recreational cannabis. Tatum told jurors he agreed to cooperate with the government in hopes of getting a more lenient sentence. He revealed how the pair targeted drivers — often young white men in rental cars with paper license plates — and fabricated their authority while conducting traffic stops in 2017.

“We made sure we didn’t call dispatch or tell anybody,” Tatum testified, describing stops that took place far outside Rohnert Park’s jurisdiction. “The more we talked about it, the more realistic and comfortable it got.”

Tatum also testified that he had been involved in earlier cannabis thefts that Huffaker didn’t know about.

On the witness stand, defense attorney Richard Ceballos asked why Tatum never told his former colleague what he had been up to. “I was ashamed and embarrassed,” Tatum replied. But that shame and embarrassment didn’t stop Tatum. He testified that he and Huffaker posed as agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives.

They seized drugs and funneled the cannabis to a dealer, William “Billy” Timmins, who received immunity and is expected to testify later in the trial.

Tatum’s testimony also revealed the personal toll of his cooperation. He recounted the moment he told Huffaker in 2022 that he was working with investigators: “He hates me. We don’t talk,” he said.

For years, Rohnert Park residents have expressed outrage over Tatum’s continued presence in the community despite his admission of wrongdoing. His sentencing has been repeatedly delayed.

On Tuesday, he told the court and Judge Maxine Chesney his future now hinges on full transparency. He is set to be sentenced in September.

The scandal traces back to the Rohnert Park Department of Public Safety’s drug interdiction team, which Tatum led until resigning in 2018. The team operated along Highway 101 — sometimes up to 40 miles outside city limits — until it was disbanded after cannabis was legalized.

But even after the team was broken up, the traffic stops continued. Prosecutors say Huffaker and Tatum used their training to identify targets and never reported the encounters. Tatum estimated they conducted five or six illegal seizures.

A pivotal moment came Dec. 18, 2017, when two California Highway Patrol officers happened upon one of their stops. Tatum testified he recognized at least one of the officers, who left after about five minutes. That brief encounter left a trace that helped investigators connect the dots after a driver lodged a complaint with Mendocino County officials.

“Looked like we had the heat on us,” Tatum said. “We couldn’t get away with it. We were in trouble.”

He testified that months later, as news coverage of another suspicious stop surfaced, the FBI reached out. He and Huffaker fabricated a police report to mislead investigators, referencing the Dec. 18 stop rather than a Dec. 5 encounter that neither officer was involved in. That lie helped launch an internal probe.

Tatum said he repeatedly lied to cover up the misconduct. He resigned from the department soon after the internal investigation began. Around the same time, then-Public Safety Director Brian Masterson also abruptly retired. Huffaker, after being found to have violated department policy, accepted a $75,000 settlement to leave the force in 2019.

He has pleaded not guilty to the federal charges.

In 2020, Rohnert Park paid $1.5 million to settle federal lawsuits filed by eight drivers who accused officers of robbing them during unlawful stops. Tatum’s testimony is expected to play a central role as Huffaker’s trial continues into next week.

Once praised for leading the interdiction team, which brought in 3,000 pounds of cannabis and $2.8 million in illegal drug money over three years, Tatum testified that the department was “overwhelmed” by the volume of cannabis seized.

But his testimony also revealed illicit behavior during that period. He admitted to burying cannabis on property along Snyder Lane and keeping some to sell. Ceballos seized on that point in an attempt to discredit him. “How many people do you think you extorted and wronged during this period of time?” he asked.

Tatum said he didn’t know. Ceballos asked if there could have been a hundred victims, and whether Tatum remembered the first time he acted irresponsibly.

He repeated he did not.

“This is over nine years ago and I’m ashamed and I took responsibility for what I did,” Tatum added. “I tried to move past the bad things I did and become a better person.”