Attorney Roger Rosen said he hasn't been told there is an indictment, but can't think of any other reason why he and Spector have been called to court.
"All the stars are lined up just right ... that's why we're going there," Rosen said.
A spokesman for the district attorney's office declined to comment on whether the grand jury issued an indictment.
Spector, 64, is suspected in the shooting death of actress Lana Clarkson in his home on Feb. 3, 2003.
Clarkson, 40, was best known as the star of Roger Corman's cult film classic "Barbarian Queen." She was working as a hostess at the House of Blues on the Sunset Strip and left with Spector the night she was killed.
Spector, famed for creating rock 'n' roll's "wall of sound" recording technique in the 1960s, is free on $1 million bail.
A grand jury indictment would preclude the need for a preliminary hearing, in which prosecutors would have to present enough evidence to hold Spector for trial. Rosen said Wednesday his client is "very disappointed" that it appears there won't be a preliminary hearing.
"He was very much looking forward to the preliminary hearing and getting the information out to the public," Rosen said. "If that had happened, I think there was a very decent chance that this case would have been dismissed."
Spector suggested in an interview with Esquire Magazine that Clarkson shot herself.