Federal district court Judge Shira Scheindlin's stunning 195-page opinion on August 12 about stop-and-frisk in New York City should be mandatory reading for every police commissioner and police chief in the United States.

In meticulous detail, Scheindlin documents how the New York Police Department violated the constitutional rights of minorities by routinely stopping "blacks and Hispanics who would not have been stopped if they were white."

New York, of course, is not unique; the problem of race-based policing exists in every urban area. In 2000, I was asked to do an examination of the Los Angeles Police Department following the Rampart scandal, which involved misconduct including police planting drugs on innocent people to gain convictions. I worked with a group of civil rights lawyers and interviewed dozens of police officers. My findings about race-based policing by the LAPD were remarkably similar to Scheindlin's conclusions about the NYPD.

Scheindlin grounded her opinion in facts that will make it very difficult for a higher court to reverse her decision. She reviewed statistics on 4.4 million police stops made between January 2004 and June 2012, and said a police forms database indicated that at least 200,000 were made without reasonable suspicion.

In 52 percent of those 4.4 million stops, the person stopped was black; in 31 percent the person was Hispanic; and in 10 percent the person was white. Weapons were seized in 1 percent of the stops of blacks; 1.1 percent of the stops of Hispanics; and 1.4 percent of the stops of whites. Contraband other than weapons was seized in 1.8 percent of the stops of blacks; 1.7 percent of the stops of Hispanics; and 2.3 percent of the stops of whites.

The problem, in part, stems from the U.S. Supreme Court's 1968 decision in Terry v. Ohio. The court, in an opinion by Chief Justice Earl Warren, held that police officers may stop and frisk an individual if there is reasonable suspicion "that criminal activity may be afoot and that the person with whom he is dealing may be armed and presently dangerous."

In other words, the traditional Fourth Amendment standard of probable cause does not need to be met to stop and frisk a person; only "reasonable suspicion" is required. "Reasonable suspicion" is a lower standard that makes it much easier for police to stop individuals.

DETRIMENT OF MINORITIES

Whenever there is significant discretion in the criminal justice system — whether in whom to arrest, what to charge or what sentence to impose — it is used to the detriment of racial minorities. The question is what can and should be done. One possibility is for the Supreme Court to reconsider Terry v. Ohio in light of 45 years of experience. In Terry, Warren approved stop-and-frisk by concluding that the benefits to law enforcement were great and the intrusion from a stop-and-frisk was minimal. Yet, there is now reason to believe the opposite is the case.

Studies cast serious doubt on the efficacy of stop-and-frisk as a law enforcement tool. University of California, Berkeley School of Law professor Franklin Zimring, in a study of policing in New York, found that the decrease in crime in that city was not linked to the stop-and-frisk policy, but rather reflected a national reduction in crime and other law enforcement efforts of the NYPD.

At the same time, there are real costs to stops and frisks based on race. Scheindlin spoke of the "human toll of unconstitutional stops" and how stops are inevitably "a demeaning and humiliating experience." As Scheindlin declared, "No one should live in fear of being stopped whenever he leaves his home to go about the activities of daily life."

It is unlikely, however, that the court will reconsider Terry v. Ohio; none of the justices has expressed an interest in doing so. Because Scheindlin did not attempt to halt the practice by NYPD officers, the question is whether adequate checks on the police are possible while continuing to allow police to engage in stopping and frisking based on reasonable suspicion.

Scheindlin appointed an independent monitor, Peter Zimroth, a partner at Arnold & Porter, a former corporation counsel and prosecutor in the Manhattan district attorney's office. The experience of other cities, such as Los Angeles, shows that an outside monitor can make a real difference in policing. In the wake of the Rampart scandal, Los Angeles and the U.S. Department of Justice entered into a consent decree that reformed many aspects of the LAPD and included appointment of an outside monitor. By all accounts, this helped to bring about major, long-needed changes in the LAPD. Scheindlin also ordered an experiment with police wearing body cameras and mandated a series of community meetings.

But it is unclear whether these steps will be enough to change the culture of the NYPD, which has not only tolerated but encouraged race-based policing. It was telling that Mayor Michael Bloomberg's response to Scheindlin's opinion was to denounce it and pledge to appeal, rather than to condemn race-based policing. In my report on the LAPD, my central conclusion was that the problems stemmed from a culture in the department that had been developed and reinforced over many years.

It is difficult to change the culture of any institution. But above all, Scheindlin's opinion is a powerful call to do just that with regard to the NYPD. And though her opinion is only about that department, it surely could be about policing in any city in America.

Erwin Chemerinsky is dean, distinguished professor of law and Raymond Pryke Professor of First Amendment Law, at the University of California, Irvine School of Law.