In the weeks after a cellphone planted by the FBI was discovered inside Men’s Central Jail, former Los Angeles County Sheriff Lee Baca, Undersheriff Paul Tanaka and other top department brass kept in constant contact with each other, a federal jury was told Monday.

But what Baca, Tanaka and Capt. William “Tom” Carey relayed to one another in those phone calls during the months of August and September 2011 is unknown, testified Leah Tanner, a special agent with the FBI. However, days and times of approximately 40 calls made among them during those months corresponded with a flurry of activity by the department to obstruct an FBI investigation into excessive use of force and corruption inside the jails, she said.

“Days when key things were happening were those days when Mr. Carey and Mr. Tanaka were calling Mr. Baca,” Tanner said.

Tanner’s testimony is at the heart of the federal government’s case against Baca, who they allege was aware of his high-ranking officers’ intentions to stop her and other agents from probing deeper into inmate abuse by deputies.

Cellphone knowledge set off activity

Prosecutors allege that when Baca, Tanaka and Carey, among others, learned that the FBI had managed to get a cellphone to inmate-turned-informant Anthony Brown to have him report excessive use of force, a series of actions was set in motion. That included allegedly falsifying Brown’s records and identity, hiding him from FBI agents and, later, threatening Tanner, with arrest at her home.

Jurors heard Tanner describe how she became part of a team to investigate allegations of inmate abuse and how she and other agents used Brown to trick a deputy into smuggling a cellphone to him. Brown used the phone to report abuse when he saw it. The phone was discovered in August 2011, inside a Doritos chip bag in Brown’s cell by deputies who were conducting a routine sweep of contraband inside the jails.

Tanner said the FBI purposely kept its investigation a secret from the Sheriff’s Department so agents could collect evidence without disruption. She learned that deputies were falsifying reports to hide their beat-downs and “drive-bys,” which occurred when a cuffed inmate was already on the ground after a beating and deputies would come by and punch and kick him.

Agent confronted at home

After Brown’s phone was discovered, Tanner said she no longer went inside the jails to conduct interviews with other inmates. But at her home one day in September 2011, two sheriff’s sergeants approached her, told her she was a suspect in a felony complaint and threatened her with arrest.

“We can do this right here,” Sgt. Scott Craig could be heard saying on a surveillance tape taken by sheriff’s investigators and played for the jury. Tanner took that to mean “that they could arrest me right there in front of my neighbors,” she told the jury.

Monday marked the sixth full day of testimony from witnesses called by the prosecution, who have charged Baca with making false statements, obstructing justice and conspiring to obstruct justice all in connection with the FBI’s jail corruption investigation.

Tanner is expected to return to the stand Tuesday to be cross-examined by Baca’s defense attorney, Nathan Hochman. Hochman said in his opening statement that Tanner, whose last name in 2011 was Marx, was a rookie FBI agent at the time of the jail abuse investigation, having been with the agency for about a year.

Hochman also has said Baca was trying to keep inmate Brown safe until he understood the motive behind the FBI investigation. The FBI, Hochman said, never told Baca what they were investigating.

Federal prosecutors expect to rest their case by the end of Tuesday. This is Baca’s second trial related to the jail corruption investigation. In December, a jury could not decide unanimously if Baca was guilty on the counts of obstruction of justice and conspiracy to obstruct justice. A mistrial was declared and prosecutors decided to try him again, but this time they included a third charge of making false statements to investigators.