He believes there is institutionalized racism among the police forces.

“The police have this prejudice that if a German of Russian descent is killed it’s because of a drugs dispute, or if a Turk is killed its because of some inner-cultural or family honor dispute,” Mr. Kolat said. “What does that mean for integration when people who become German citizens expect the state to protect them but then they discover that it doesn’t?”

Police officials have denied that there is systemic racism among their ranks.

Still, the investigations committee is trying to discover how the police failed to connect the dots between the neo-Nazi group and the killings. The Zwickau cell and other groups had, after all, been under constant observation by the intelligence services.

“This certainly was a failure for what the domestic intelligence service and all the other security service are accountable for,” Interior Minister Hans-Peter Friedrich said recently.

The police, too, had recruited informers but somehow failed to discover that the N.S.U. cells had weapons and that the three neo-Nazis from the Zwickau cell had been planning the killings for some time.

An even more disturbing aspect is that on Nov. 12, 2011, a day after it became public that the N.S.U. was suspected in the killing of the Turks, the Greek and the policewoman, the office for the Protection of the Constitution, Germany’s domestic intelligence agency, destroyed files relating to the case. Those files included details about recruiting far-right informants.

Interior Ministry officials said the files had already been due to be shredded as a matter of data-protection policy. Still, even committee members say it seems more than a coincidence that those files should be destroyed just at the investigations began.

“Informants do not have clean information,” said Petra Pau, who is also on the parliamentary committee. “That recruitment system should be scrapped.”