RECIFE, Brazil — The name was on the tip of Rosario Lapa's tongue, but it stubbornly stayed there. She tapped her forehead to try to shake it loose, then turned to her friends for help.
"What do they call the death squad here?"
Five middle-aged women, all of whom were visiting a church in their neighborhood's central square, answered in imperfect unison: "The Thundercats."
If you want someone killed in this working-class district, that's the name to remember. Almost everyone in the Jardim Sao Paulo neighborhood has heard of the group, even those who have never sought out its members.
Officials say that death squads in the murder-for-hire business are responsible for a majority of the killings in the state of Pernambuco — Brazil's deadliest, based on figures for homicides as a percentage of population. Because the rosters of those squads routinely include police officers and other prominent residents, talking freely about their influence has long been considered an invitation to trouble.
"I'm pretty brave, but it's scary to think about speaking out if you see them committing crimes — they could do something to my son or my husband, and that would break my world," said Lapa, 63. "There's always a police officer involved, so if you have seen something, how can anyone be trusted?"
The presence of such squads has plagued many parts of Brazil for years, but growing public demand for justice last year prompted officials here to create the first large-scale, regional task force to combat them.
Now, authorities are working against authorities in what resembles an enormous internal affairs investigation. In the past year, about 200 people have been nabbed in several high-profile busts of various squads in Pernambuco, and many of those arrested have been police officers and other officials.
The Thundercats were one of the first targeted last year, and the break came when a mother's concern for her son proved stronger than the group's stranglehold on a hushed-up public.
"The death squads have tools to hide their actions, either through ties to public offices or by creating a veil of fear," said Rodrigo Pellegrino de Azevedo, the state's secretary of human rights. "But this one mother came directly to the governor and told him about one man in the Thundercats who wanted to kill her son."
The subsequent investigation into the group led to dozens of arrests, mostly police officers and local business owners. One of those arrested was an aide to a state legislator, who also happened to be a relative of the state's previous governor, Pellegrino de Azevedo said. In addition to committing murders, the group would force residents to pay a "protection fee" to guarantee that their houses would not be robbed, according to state officials.
In November, the task force used telephone taps, banking records and other evidence to arrest 34 more people — including police, merchants and a lawyer — for their roles in two death squads accused of killing about 200 people. Another squad arrested last year went by the name "Murder, Inc.," and police at the time told reporters that the group might have been responsible for up to 1,000 homicides.
The price of the murders ranged from about $600 to $3,000 each, according to federal police. The victims included people who were late on extortion payments and debts, as well as people involved in personal disputes with those who contracted the killings.
The groups' ties to public institutions have helped create a culture of impunity. Military police affiliated with the squads often arrive early at crime scenes to cover up evidence, according to officials. The U.N. special rapporteur on extrajudicial executions, Philip Alston, visited Pernambuco late last year and reported that only 3 percent of the state's homicides were tried in court. He found that about 2,000 files submitted to the state's public prosecutor were thrown out because the police in Pernambuco had delayed action for so long that the statute of limitations had expired.
A "reliable estimate is that 70 percent of all homicides are committed by death squads," Alston wrote in a summary of his visit. "The 197 people who have been arrested this year (2007) for death squad activity represent only the tip of an iceberg."
The man in charge of the task force targeting the death squads is Servilho Silva de Paiva, the state's secretary of social defense. He said that his office is working to come up with credible statistics to measure the extent of the squads' reach. In the meantime, he acknowledged that the percentage of crimes influenced by the squads is "high."
"For years, the governments here never wanted to show how bad the problems were," he said.
According to Silva de Paiva, the absence of a strong government presence and reliable social services allowed the squads to flourish. In the 1990s, understaffed police forces and an inefficient judiciary contributed to a feeling of lawlessness here. Many in the middle classes — and some in law enforcement — began viewing death squads as an alternative form of justice.
One of the first jobs of the task force was to strengthen the internal investigation units of the police to root out corrupt officers. A witness protection program also has been strengthened to try to give victims more confidence to speak to authorities.
It is still too early to determine whether the task force's arrests will have any measurable effect on violence here. Some observers say greater efforts are needed to define the problems before they can be solved.
"It's true that there is now a real effort to diminish the groups, but I don't think there has been a substantial change, yet," said Valdenia Brito, a lawyer with the Cabinet of Legal Support to Popular Organizations, a human rights group that has worked on the issue for years. "There is so much that we don't know. We don't even have a clear idea of the number of death squads that exist."