The last time Michael Armstrong was appointed to monitor police corruption in New York City was in 1970, and more than a few cops were prosecuted for working “on the pad,” collecting “tips” from store owners, numbers runners, prostitutes, and others.

More than three decades later, Mr. Armstrong, a noted criminal-defense lawyer who served briefly as Queens district attorney, has been appointed by Mayor Bloomberg to run the city’s embattled police watchdog, the Commission to Combat Police Corruption.

Now, Mr. Armstrong, 72, told The New York Sun, corruption is significantly more difficult to pinpoint.

Before his appointment, the commission was targeting such areas as background checks for civilians and the accuracy of crime statistics. Mr. Armstrong declined, however, to speculate on the areas of the Police Department he might choose to probe.

Accountability within the department, especially within the Internal Affairs Bureau, he said, has improved drastically since he was the chief counsel to the Knapp Commission, which exposed widespread misconduct among the rank-and-file police officers.

“The corruption then was so pervasive it was hard to miss,” Mr. Armstrong said. “It was everywhere you looked. There was a fog of corruption.”

Now, a fog of ineffectiveness, critics say, as well as a clashing of heads with department brass over jurisdictional issues, has defined the independent efforts to monitor anti-corruption efforts. While the number of reported felony crimes in New York continues to drop beyond the expectations of criminologists, the number of complaints made against police officers for misconduct has risen over recent years, and legal payouts as a result of police misconduct lawsuits have increased.

Officials of the commission have said the department has not provided records necessary for it to compile regular reports, and they have complained that the commission has become little more than a “a letter-writing agency.”

A few months before resigning as chairman, Mr. Armstrong’s predecessor, Mark Pomerantz, a former federal prosecutor, testified at a City Council hearing that the commission had been unable to issue some planned reports because department officials had routinely failed to provide documents such as employee records or police records. Without subpoena powers, Mr. Pomerantz said, the commission has lost effectiveness.

A police spokesman, Paul Browne, said the department had complied with legitimate requests from the commission for information. Information was not provided, Mr. Browne said, in cases when police officials felt the subject area was outside the commission’s authority.

For years, some city lawmakers have attempted to strengthen the commission by giving it subpoena power. But those legislative attempts have failed.

“We have some real problems here,” the chairman of the City Council’s Committee on Public Safety, Peter Vallone Jr., said of continuing friction between the commission and the Police Department. Of Mr. Armstrong’s role at the commission, Mr. Vallone, a Democrat of Queens, said: “What we need is someone who has a good relationship with the Police Department and someone who is independent at the same time.”

Mr. Armstrong said he was not worried about jurisdictional disputes or potential problems receiving documentation from police headquarters.

“I think Ray Kelly and I understand each other very well,” Mr. Armstrong said of the police commissioner, a fellow Bloomberg appointee.

Mr. Browne, the police spokesman, said Mr. Armstrong possessed “outstanding credentials and experience.”