The final witness, FBI Agent Joe Robuck, testified the officer, Arthur Bruce Tesler, told him he would rather cover up misconduct than be called a rat, The Atlanta Journal-Constitution reported.

Kathryn Johnston died in a barrage of police bullets when she pulled out a gun as officers broke down her door in November 2006. Robuck said Tesler lied convincingly during the early FBI investigation of the raid but later acknowledged he had gone along with a cover-up because he was "the low man on the totem pole."

Two officers have pleaded guilty to voluntary manslaughter for their role in the raid in 2006 at Johnston's house. Tesler, who was covering the back of the house and never fired his gun, faces charges of lying in an official investigation and violating his oath of office.

Robuck said Tesler admitted the no-knock warrant was based on misleading stories from officers who lied about their dealings with an informant. He said marijuana also was planted in Johnston's house in an attempt to justify the raid.