Readers might be wondering if we at ProPublica are just a little obsessed with New Orleans, specifically what happened after Katrina. Over the past year, we’ve devoted substantial energy to examining what happened when the floodwaters battered two important institutions: Memorial Medical Center and the New Orleans Police Department.

These may seem like local matters. They’re not. The performance of a police force or a hospital under the crushing pressures of a catastrophe has implications for every police force and hospital in the country.

ProPublica’s pursuit of these stories began by coincidence; both reporters had been separately working on them when they were hired. But we felt they were both worth backing in a big way and committed what amounts to 10 percent of our reporting staff to this work for an entire year.

Here’s why:

Four years after the storm, New Orleans faces a challenge that has echoes of what I observed when I covered Eastern Europe from 1990 to 1993. Then, people who had lived for decades under the weight of Communist repression had an instinctive, understandable reluctance to probe a past in which many of their fellow citizens were heroic, but some were not. The first democratically elected prime minister of Poland announced in his first days in office that the nation should look forward, not back, and should draw a “thick line” between the ugliness of the past and the promise of a bright future.

Investigative reporters tend to think otherwise. Unresolved stories have a corrosive effect on communities. And the people have a right to know some facts, such as when political leaders or institutions are responsible for the deaths of fellow citizens. Gradually, the former Communist countries, including Poland, decided that however painful it might be, addressing the past was necessary.

The same applies to New Orleans. At the end of 2008, A.C. Thompson’s shoe-leather reporting on police conduct and possible vigilante attacks during Katrina against African-Americans prompted the U.S. Justice Department to launch multiple civil rights investigations of the New Orleans police.

In the months since, prosecutors have hauled a parade of witnesses before a federal grand jury, which is expected to return indictments early next year. There is talk that the long-troubled New Orleans police department could be taken over by federal authorities.

Sheri Fink’s reporting on how a few doctors at Memorial injected at least 17 patients with high doses of morphine or sedatives — or both — in the days after the storm raised searing questions about the rationing of care in a catastrophe. Her work on those events has grown into her national examination of the planning,  or lack of it, that the U.S. Veterans Administration and states from Florida to New York have done to deal with disasters, notably the pandemic flu .

A.C. Thompson’s work raises an equally basic question: Can the police be trusted to investigate themselves?

This week, ProPublica, The New Orleans Times-Picayune and the PBS series “Frontline” launched a major reporting effort to dig even deeper. The continuing investigation began with a four-part series, co-published in the Times-Picayune, and on “Frontline,” examining the New Orleans Police Department’s record during the week immediately following Katrina. In the storm’s aftermath, the police shot at least 10 civilians. Our series, which has focused so far on three of these bloody incidents, shows that the department made only cursory efforts to determine whether these shootings were justified.

Defenders of the police note that it was impossible to observe all the niceties of evidence collection in the immediate aftermath of a devastating hurricane. But they could not explain why interviews of officers who fired shots – conducted months after the floodwaters receded – lasted as little as seven minutes. The work on this story is continuing and includes direct appeals to witnesses who might shed more light on several of the more mysterious police shootings. We believe such collaboration between national and regional media is part of the future of journalism and will bring new facts to light in 2010.