THE WEEKEND of Sept. 27 brought anti-globalization demonstrations and, if D.C. Council member Kathy Patterson's charges are true, a serious blemish to the reputation of the Metropolitan Police Department.

According to Mrs. Patterson, a police department internal affairs report on the handling of last fall's World Bank-IMF protests concluded that even though nearly 400 people in a downtown park were arrested and charged with "failure to obey a police order," the arresting officers had neither given orders nor seen orders disobeyed. The intent of the police action, she claims the report suggests, was never to disperse the crowd but instead to surround the park and sweep up and arrest those inside. What's more, many of those arrested were bound wrist to ankle so they couldn't stand up or lie prone, and some were detained in excess of 24 hours. In the end, no one was prosecuted, though some protesters paid fines. The city, it turns out, could wind up paying as well. September's mass arrests at Pershing Park are now the subject of litigation.

How did it come to this? For many years, D.C. police officers have enjoyed a well-deserved reputation for their deft handling of large public demonstrations. Thousands of people have managed to mass in the city, petition their government or protest public policy, and then depart town without leaving lawsuits behind. We would like to think that the combination of the city's respect for constitutional rights and a well-led and highly professional police force helped produce those years of successful demonstrations. Today, however, Mrs. Patterson, who chairs the Judiciary Committee, which oversees the police, contends that the department has gone off the track, and she holds Mayor Anthony A. Williams responsible. In a statement last week, Mrs. Patterson charged the mayor with violating the public trust by failing to act promptly on the internal affairs report, which he received on Jan. 25. The arrests, she said, were "preemptive and wrongful," the detentions were inhumane, and officers signed arrest forms that were inaccurate "on their face." "The Metropolitan Police Department, under Mayor Tony Williams," she said, "stands compromised by their own actions last fall and by the mayor's inaction since that time."

Yesterday Margret Nedelkoff Kellems, deputy mayor for public safety and justice, said the police department is already working on changes in policies and procedures involving mass arrests and methods for restraints to prevent a recurrence of September's problems. At this stage, she added, Police Chief Charles H. Ramsey is weighing steps to be taken if it is found that officers in the Pershing Park arrests failed to follow established policy. No time limit has been set, but Ms. Kellems said the mayor is pressing the chief for a final report.

That is a languid mayoral response given the seriousness of the alleged violations. Keeping the city safe is not a mandate to arrest citizens without probable cause. Past D.C. police departments have managed to handle demonstrations while respecting the Constitution. This department, under Mr. Williams, is no less accountable.