On Tuesday, Oscar Pistorius' defense lawyer Barry Roux revealed Johnson's cellphone number in court. Before testifying on Wednesday, Johnson said he felt his "privacy has been compromised."
Johnson and his wife Michelle Burger live 193 yards from the Olympian's home.
Burger, a university lecturer who was the first witness in the Pistorius' murder trial, broke down in tears Tuesday, saying she still remembers the terrified screams of a woman on the night the double-amputee athlete killed his girlfriend.
Roux cast doubt on Burger's testimony and suggested that a scream she heard was actually Pistorius.
The trial continues.