Mr. Floyd’s testimony on Monday in Federal District Court in Manhattan about his encounters with the police, in 2007 and 2008, came during the first day of a trial in a class-action lawsuit over whether the New York Police Department has been unconstitutionally stopping hundreds of thousands, or even millions, of black and Hispanic men and boys in the street.
While the judge deciding the case, Shira A. Scheindlin, will consider the significance of the soaring number of recorded street stops by the police over the last decade, the testimony on Monday focused on just three specific encounters. Two were police stops of Mr. Floyd, now a 33-year-old medical student in Havana, and the third was a stop of a Manhattan teenager, Devin Almonor, who testified that the police stopped, frisked and ultimately arrested him when he was 13, as he walked home in Hamilton Heights.
Both Mr. Floyd and Mr. Almonor are black, and Mr. Almonor, now 16, testified that he could think of “no other reason” besides race that police officers would have stopped him on that March night in 2010. A lawyer for the city, Suzanna Publicker, suggested that the cellphone Mr. Almonor had in his front pocket might have “created a bulge,” hinting that it might have resembled a concealed weapon to a police officer.
None of the officers involved in the stops testified on Monday.
The trial, which is expected to last six weeks, is one of the most significant courtroom tests of a crucial Bloomberg administration policy, and the stakes are high for the city. Lawyers for the plaintiffs are asking Judge Scheindlin to create “a process for obtaining community input” to influence the Police Department’s stop-and-frisk practices and also to appoint a monitor to ensure that the department’s policies comply with the United States Constitution.
During opening arguments on Monday, a lawyer for the city, Heidi Grossman, said that plaintiffs sought “to divest the N.Y.P.D. of control over how the N.Y.P.D. investigates crime.”
While acknowledging that “errors and mistakes may happen in the area of stops and frisks,” Ms. Grossman said there was no evidence of a “constitutional deficiency” or a “widespread pattern of illegal stops.”
The reason the stops overwhelmingly involved black and Hispanic men was not the practice of racial profiling, she said, but the department’s use of “a disproportionate share of resources on minority neighborhoods, where crime is highest.”
That, Ms. Grossman said, “is the nature of hot-spot policing.” As crime across much of the city has drastically receded over the last two decades, Ms. Grossman said, the department has dispatched officers to places where crime stubbornly persists.
But a lawyer for the plaintiffs, Darius Charney of the Center for Constitutional Rights, said police officers were stopping people without any legitimate grounds for suspecting them of criminal behavior.
“What the N.Y.P.D. calls proactive, the black and Hispanic residents of this city have experienced as arbitrary, unnecessary and unconstitutional harassment,” Mr. Charney said.
Mr. Almonor said he had been stopped after spending the day riding a bike and playing video games with a friend. After walking the friend to his bus stop and waiting with him there, Mr. Almonor headed home, pausing for a time in front of a bodega after running into friends.
As Mr. Almonor continued on his way, two plainclothes officers emerged from a car to question him.
“I told them I was 13,” Mr. Almonor said. “After they patted me down, they pushed me up against the car.”
He added that the officers then handcuffed him. “I was crying,” he said.
The situation escalated, and both of Mr. Almonor’s parents were later arrested at the 30th Precinct house in East Harlem, where they had gone to demand the release of their son, though that was not discussed in court on Monday. Mr. Almonor’s father, a retired officer, was subsequently tried and acquitted on charges of punching a female police officer during the confrontation over his son’s arrest.