Detective Mark Lillienfeld of the Los Angeles County sheriff's homicide unit put on gloves before removing the gun from an envelope because there was still blood on it. The gun was found at Clarkson's feet.
Using photos shown by prosecutor Pat Dixon, Lillienfeld pointed to a bureau to one side of the chair where Clarkson's body sat slumped in a foyer near a door of Spector's home.
One of the bureau's drawers was open and visible inside was a holster, which Lillienfeld said was later shown to fit the gun.
Clarkson, 40, died about 5 a.m. on Feb. 3, 2003, from a single shot fired with the gun in her mouth. She had accompanied Spector on a chauffeured ride to his Alhambra mansion after meeting him at her job as a hostess at the House of Blues just hours earlier. The defense claims that Clarkson killed herself.
The prosecution previously called several women from Spector's past to testify that he had threatened them with guns when they tried to leave his presence.
Dixon had Lillienfeld point out for the jury a leopard-print purse with long straps hung over Clarkson's right shoulder. Her right hand rested atop the purse, which sat on the floor.
The coroner who conducted Clarkson's autopsy and ruled her death a homicide testified previously that the presence of the purse on her shoulder was one of the non-medical observations that led him to rule out suicide. He said it was not typical of a suicide scenario.
Lillienfeld testified that he spent 30 hours at the scene over two days and the prosecutor asked him if he had ever had any trouble understanding anyone he conversed with there because of noise from a fountain in the motorcourt.
The detective said he had no trouble understanding anyone.
The issue was raised earlier in the trial when the defense sought to challenge testimony by the chauffeur who said that Spector came out of his house with a gun in his hand and said, "I think I killed somebody." The chauffeur was near the fountain at the time.
Spector, 67, rose to fame with the hit-making "Wall of Sound" recording technique in the 1960s. Clarkson was best known for her role in the 1985 movie "Barbarian Queen."