For Cyrus R. Vance Jr., the Manhattan district attorney, the verdict was an unsatisfying conclusion. The decision, after a trial that lasted almost two months, also comes at a critical juncture for an office that is navigating the biggest case of Mr. Vance’s brief tenure: the sexual-assault charges against Dominique Strauss-Kahn, the former managing director of the International Monetary Fund.

The jury’s decision also underscores the difficulty of obtaining favorable results for women who say they were sexually assaulted, and who often are subjected to scrutiny and skepticism that keep many of them from speaking out. In this case, defense lawyers pounced on the credibility of the woman because she was very drunk on the night in question and did not remember many details.

After the verdict, Officer Moreno said outside the courthouse that his accuser, who has a $57 million lawsuit pending against the city and the officers, was “mistaken and confused,” and that “she made the whole thing up.”

But the officer, who appeared tense and tight-faced, also said he was not angry.

“I’m glad it’s over,” he said. “It’s a lesson and a win.”

When a reporter asked Officer Moreno what he meant by lesson, his lawyer, Joseph Tacopina, interjected, saying, “Well, we’ll just leave it at that.”