In the early morning hours of April 12, Louis Calixto allegedly pummeled a woman on an East Village sidewalk so fiercely that the blows could be heard over the late-night noise of the city street.

But after the victim declined to testify, Mr. Calixto moved to dismiss the third-degree assault charges against him, contending that the prosecution could not establish the element of “physical injury” based solely on the testimony of an eyewitness, who had allegedly witnessed the attack and had agreed to testify against him.