“Did there come a time when the police officers searched the bag by going through the lining?” she asked.

In pursuing this line of questioning, Judge Scheindlin is also expanding the constitutional focus of the trial to include the other aspect of the Fourth Amendment at issue: the reasonableness of the police search, rather than just the reasonableness of the police’s initial detention of the person.

As a matter of law, the police are allowed to frisk for their safety when they have stopped someone whom they reasonably suspect of engaging in criminal activity and, in addition, is thought to be carrying a concealed weapon. In a landmark 1968 decision recognizing the right of police officers to conduct stop-and-frisks, the Supreme Court held that frisking was for “the protection of the police officer and others nearby.” The court also said that “it must therefore be confined in scope to an intrusion reasonably designed to discover guns, knives, clubs, or other instruments for the assault of the police officer.”

Judge Scheindlin has directed similar questions toward officers, asking them about the circumstances that led them to frisk a person in the first place — slightly more than half the recorded street stops in New York City result in frisking — and what the frisking entailed.

“Could you explain how you conducted the frisk?” Judge Scheindlin asked one officer.

“I patted the outside part of his, of his clothing, ma’am,” the officer, Eric Hernandez, responded, testifying about a 2008 stop for suspected burglary in the Bronx.

In the landmark 1968 decision, in Terry v. Ohio, the Supreme Court observed that frisking, even when limited to a pat-down, was far more than a “petty indignity” unworthy of Fourth Amendment protection. Rather, the court found, it “is a serious intrusion upon the sanctity of the person, which may inflict great indignity and arouse strong resentment, and it is not to be undertaken lightly.”

Testimony from the trial is underscoring just how intrusive that experience can be from the perspective of the person being frisked. Mr. Peart, for instance, testified about an earlier stop that had led to his being ordered to the ground at gunpoint. He struggled for words to describe what happened next: “They patted over my basketball shorts and I was touched.”