Judge Larry Fidler ruled Wednesday that forensics expert Henry Lee "did recover an item that was flat, white and irregular around the edges," the Los Angeles Times reported Thursday.
The music producer is charged in the 2003 death of actress Lana Clarkson, found shot in the mouth in his home. He pleaded not guilty, saying Clarkson shot herself.
In a hearing outside the jury's presence, three people testified they saw an object at the crime scene and two of the three said they saw Lee pick it up.
Prosecutors said the object was a piece of Clarkson's acrylic fingernail, which could show her hand was in front of her face, not holding the gun.
Because he couldn't determine whether it was a fingernail, Fidler said jurors could be told an item was missing, and decide for themselves what it may have been and whether Lee withheld information.
Fidler said jurors would be told not to hold the matter against Spector because no evidence indicated he knew.
Spector's attorneys said Lee still was expected to testify.