LOS ANGELES — A mistrial was declared yesterday in the murder case against music producer Phil Spector when the jury reported for a second time that it could not reach a verdict on whether he killed actress Lana Clarkson more than four years ago.

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 about early February 3, 2003.

Mr. Spector and his wife, Rachelle, left the courthouse shortly after the mistrial.

The prosecution did not immediately say whether it would seek a retrial. A hearing was set for October 3. The jury foreman told Superior Court Judge Larry Paul Fidler the split was 10–2 but did not say which way the panel leaned. A week earlier, the foreman had reported a 7–5 split.

The jury had met for about 44 hours over 12 days since getting the case September 10.

After the initial deadlock, the judge 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 Mr. Spector forced Clarkson to place the gun in her own mouth.

Judge Fidler polled the jury, and each member agreed that a unanimous decision was not possible.

“At this time, I will find that the jury is unable to arrive at a verdict and declare a mistrial in this matter,” the judge said.

Mr. 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.”