A witness testified Monday that cell phone records tie Andre Grier to the 2016 murder of Biancha Horton.
Grier is facing a possible death penalty sentence in the case.
Courtney High earlier pleaded guilty and got a life prison sentence. The third defendant, Charles Shelton, died at the county jail.
Ms. Horton had been set to testify against Cortez Sims in his murder trial in the incident in which he shot her daughter Zoe.
Ms. Horton was shot several times and her body was dumped on the side of the road.
Detective Jeremy Winbush, who is with the Chattanooga Police Department but works with the FBI Task Force, said a "cell tower dump" was carried out to try to find phone numbers associated with three locations at a specific time period.
They were the office where Ms. Horton worked on Quintus Loop, her home at the Stone Ridge Apartments on 37th Street, and the location where her body was found on Elder Street near the East Ridge tunnel.
He said two numbers showed up at all three locations around the time of the murder. One was tied to Shelton and another to Grier.
Detective Winbush said the same phone number was used for inmate calls to Grier. He said one of the callers from prison was a former member of the Athens Park Bloods.
The detective said prior to obtaining the cell phone records that authorities "had some persons of interest. We were just trying to get a little more information."
The defense is trying to get the cell phone evidence thrown out, citing a recent court ruling.
The Grier trial was set for March, but it has now been delayed to October. The jury will be selected in Anderson County.
Judge Boyd Patterson is presiding.