Saturday's result was a victory for the comedian, who avoided up to a decade in prison, but the district attorney said his office would seek a verdict in a second trial.
"Just because a verdict is not reached in one case doesn’t mean it won’t be the next time around,” District Attorney Kevin Steele said at a news conference.
About 60 women have accused Cosby of sexually assaulting them, effectively ending the long career of the entertainer once known as "America's dad" for his role in the 1980s television hit "The Cosby Show." The case was the only one to result in a criminal trial, largely because the other accusations are now too old to prosecute.
After the mistrial was declared, Cosby and his legal team gathered outside the courtroom.
"This is what happens, juries are stuck when a prosecutor seeks to put someone in prison for things that are simply not presented in the courtroom,” said Angela Agrusa, one of Cosby's lawyers.
While Agrusa spoke, Cosby stood silently behind her, his head occasionally tilting back, looking toward the sky.
A spokeswoman then read a prepared statement from Cosby's wife Camille, who has steadfastly stood by her husband over the years, even after the accusations against him piled up.
"Historically people have challenged injustices. I am grateful to any of the jurors who tenaciously fought to review the evidence, which is the rightful way to make a sound decision," the statement said.
It also sharply criticized the judge and prosecutors for pursuing the case.
"How do I describe the district attorney? Heinously and exploitatively ambitious," the statement said. "How do I describe the judge? Overtly arrogant and collaborating with the district attorney."
The mistrial was a blow to the dozens of women who have said they were sexually assaulted by Cosby. Several accusers were in court all week awaiting a verdict and wearing buttons that read "We Stand in Truth."
"We can never underestimate the blinding power of celebrity, but justice will come," said Gloria Allred, an attorney who represents many of Cosby's accusers.
Cosby has said any sexual activity was consensual. He still faces at least four civil lawsuits from at least 10 accusers.
Cosby's starring role as beloved dad Heathcliff Huxtable in "The Cosby Show" made him a household name, bolstering a reputation built on years of family-friendly standup comedy routines.
His popularity also made him an in-demand product endorser, and he appeared in commercials for Jell-O, Coca-Cola, Ford and others.
He co-starred in the 1960s espionage show "I Spy," the first black performer to star in a weekly American TV dramatic series.
Cosby said in a radio interview before the trial he hoped to resume his performing career after the Constand case was resolved.
The jury appeared unable to agree on which version of the night in question to believe: Constand's or Cosby's. They spent days asking to have testimony read back, including Constand's testimony at trial as well as the first report she made to police in 2005.
They also reviewed statements Cosby made about the incident under oath during Constand's civil lawsuit in 2005 and 2006. Cosby chose not to testify at trial.
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