(Damian Dovarganes ~ Associated Press)
The prosecutor's office announced it would seek to retry Spector, and the family of the actress also pledged to press on.
"We will not rest until justice is done," said John C. Taylor, a lawyer for the family.
Spector and his wife, Rachelle, left the courthouse shortly after the mistrial. The producer's attorneys later met with the jury.
"We thank the people of Los Angeles for keeping an open mind and the jury for their very hard work and their willingness to share their thoughts with us," defense attorney Linda Kenney-Baden said after the meeting.
The mistrial came after months of a trial in which jurors had to decide who pulled the trigger of a revolver -- leaving no fingerprints -- that went off in Clarkson's mouth early Feb. 3, 2003. The jury had met for about 44 hours over 12 days since getting the case Sept. 10.
A week ago, the jury foreman had reported a 7-5 split. After that, Superior Court Judge Larry Paul Fidler withdrew a jury instruction that he decided misstated the law and issued a new one giving examples of what panelists could draw from the evidence, including the possibility that Spector forced Clarkson to place the gun in her own mouth.
Fidler polled the jury, and each member agreed that a unanimous decision was not possible.
Some jurors agreed to talk to reporters at the courthouse but did not give their names. The foreman would not say which way he voted; the other two said they voted for guilt.
One juror said the holdouts argued over whether Clarkson was suicidal and that the entire jury would have liked to see a psychological profile of the actress. Another juror was troubled by what Spector, who did not call 911, did in the 40 minutes between the death and the time police arrived.
"He acted like a guilty man," the juror said.
The foreman noted that the "inability to reach a decision is controversial to most."
"Even on the jury there's deep regret that we were unable to reach a unanimous verdict," he said.
The mistrial also disappointed prosecutors.
"We will seek the court's permission to retry the case and begin immediately to prepare for a retrial," prosecutor Steve Cooley said in a statement. A hearing was set for Oct. 3.
Prosecutors had charged Spector under a second-degree murder theory that did not require premeditation or intent.
They called women from his past who claimed he threatened them with guns when they tried to leave his presence, and a chauffeur who testified that on the fateful morning Spector came out of his home with a gun in hand and said, "I think I killed somebody," while Clarkson's body sat slumped in a foyer chair behind him.
The defense countered with a scientific case, suggesting Spector did not fire the gun and offering forensic evidence that she killed herself -- either intentionally or by accident. Gunshot residue on her hands, blood spatter on his coat and the trajectory of the bullet were the subjects of weeks of testimony from experts.
Spector, 67, rose to fame in the 1960s with the "Wall of Sound" recording technique, which revolutionized pop music. Clarkson starred in the 1985 cult film "Barbarian Queen."
Their life stories reflected different sides of the pop culture landscape.
The breadth of Spector's contributions to popular music in the 1960s and early 1970s was astounding. Early in his career, he produced hits including "He's a Rebel" and "Be My Baby," which made pop stars of the Crystals and the Ronettes.
Later, after the Beatles shelved the tapes from some of their last recording sessions, he turned them into their final album, 1970's "Let it Be." From there, he went on to produce critically acclaimed solo albums by John Lennon and George Harrison. He also co-wrote and produced the Ben E. King standard "Spanish Harlem" and the Righteous Brothers' "You've Lost That Lovin' Feelin'," cited by BMI as the most-played song in the history of American radio.
But by the time he met Clarkson, the music industry wunderkind who struck it rich in his teens and changed the face of pop music had aged into an eccentric, reclusive millionaire with a castle in the suburbs.
Clarkson, 40, was an ambitious dreamer, a statuesque beauty who idolized Marilyn Monroe and chased fame but was beaten down by rejection. Friends testified that she was at the end of her rope financially and humiliated by having to take a hostess job at the House of Blues, where she met Spector.
Jurors heard of her decision to go home with Spector for a drink after the club closed at 2 a.m. Little more than three hours later, she was dead.
What happened in those three hours was never clear. Spector did not testify, and prosecutors stated no motive for him to kill her other than her apparent decision to leave the house.
No prosecution forensic expert was able to place the gun in Spector's hands. But blood spatter on his coat and in his pants pockets were analyzed by prosecution experts to suggest that showed he was the shooter.
Defense experts said he stood too far away to have shot her. Blood spatter, they said, can travel up to 6 feet.
The defendant's changing appearance during the case was a reminder that this was a show business figure on trial. During pretrial, Spector arrived in a stretch Hummer, his hair frizzed out. For trial, he adopted a blond pageboy reminiscent of the early Beatles. But his wife, who said she styled his hair, later changed it to a short, tousled and darker look.
Rachelle Spector, 27, whose Web site says she is a singer, songwriter and trombone player, married Spector nearly a year ago and was with him every day of the trial.
The couple usually dressed in color-coordinated outfits. Spector wore long, foppish frock coats with vests, colorful shirts and ties. A diminutive figure, he always wore boots with high Cuban-style heels. Rachelle Spector wore stiletto heels, and the couple appeared to totter as they walked down the hall flanked by bodyguards.
Jurors saw a different side of the couple when they visited Spector's home for a court-supervised jury tour. The Spectors stood silently arm in arm, dressed in casual clothes, as jurors surveyed the scene of Clarkson's death.
In the last days of the trial, Rachelle Spector gave a TV interview defending her husband and was scolded by the judge and told to stop talking or face contempt charges.
On Tuesday, authorities revealed they were investigating a posting on a "Team Spector" page on MySpace.com that said "The EVIL Judge should DIE!!!!" and was signed "xoxo Chelle." A Spector defense attorney said Rachelle Spector denied having anything to do with the posting.
Associated Press writers Robert Jablon and Raquel Maria Dillon contributed to this report.