RIO DE JANEIRO (AP) — Six years ago, Elizabeth Martin's nephew Joseph was shot and killed by an off-duty police officer while out celebrating his 30th birthday in Rio de Janeiro. Now, Martin has a message for the hordes of foreigners set to descend on Brazil for next year's World Cup: The next Joseph Martin could be you.

Within Brazil, police have long been notorious for their links to organized crime, use of heavy-handed tactics including torture and even summary executions. Citizens often approach officers warily if at all, put off by the violent behavior of some police.

Martin, whose nephew was gunned down following an altercation with police over a stolen purse, worries that foreigners oblivious to Brazilian officers' reputation could unwittingly stumble into the kind of scuffle that cost Joseph his life. Although police violence in Brazil overwhelmingly targets the country's poor and rarely affects foreigners, Martin has launched a campaign, "Don't Kill for Me: Safe Games for All," aimed at raising international public awareness of the issue — especially ahead of the wave of foreign visitors expected for the World Cup and the 2016 Olympics.

"I think of police brutality as Brazil's dirty little secret," Martin said in a phone interview from her home in Massachusetts, where she stays in close contact with Brazil-based human rights campaigners and organizations representing the families of those killed by police. "People outside of Brazil have drunk the Kool-Aid of Brazil being this economic success story with beautiful beaches and bikinis and this side of it just isn't discussed, it isn't known."

Human rights campaigners and international organizations alike have long condemned Brazil's police for routinely carrying out summary executions — often officially explained away as suspects "killed while resisting arrest." A 2009 report by the U.S.-based group Human Rights Watch estimated police killed about 11,000 people in Brazil's two largest cities, Rio and Sao Paulo, from 2003 to 2009, far more than the number of non-fatal civilian injuries and police fatalities in those same areas of operation. A damning 2008 United Nations report blamed police for a "significant portion" of the country's approximately 48,000 annual slayings the year before.

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During protests over the past months, the U.S. Embassy issued travel advisories warning visitors to avoid demonstrations because of possible violence between police and demonstrators. The British government also warned of violence at demonstrations.

Law enforcement authorities insist they've made great strides in reining in rogue officers, and indeed, Rio and other metropolises have seen a significant decline both in overall murder rates and "acts of resistance," or people killed by police while allegedly resisting arrest. In Rio state alone, acts of resistance fell from their peak of 1,330 in 2007 to 415 last year, according to the state's Institute of Public Security statistics agency, though some critics contend police are "disappearing" victims by hiding their bodies. That happened in a recent high-profile case involving a slum dweller whose apparent torture and killing by police sparked protests.

Roberto Alzir Dias Chaves, a state sub-secretary for mega-events, says there's been a sea change in police tactics, which he credits for reducing the number of police shooting cases.

"Our numbers are still high, without a doubt," acknowledged Alzir. "We could like to see much lower numbers, but we have to understand that this is part of a process. . These are the first steps, we're still at the beginning of this process, but we've made great strides."

While officers used to be rewarded for using lethal force, earning cash bonuses for killing suspects as recently as around a decade ago, a quotas system put in place in 2009 now gives bonuses to the units with the lowest lethality rates. Earlier this month, Rio state shelled out nearly $26 million in bonuses to units that registered the biggest fall in police killings as well as a range of crime statistics in the first half of the year.

Joseph Martin was plunged headlong into Brazil's police brutality drama in May 2007, when an off-duty officer, Joao Vicente Oliveira, detained a boy who'd snatched a purse belonging to one of Martin's friends, who were out celebrating his birthday at a popular Rio nightspot.

The American, who had been living in Brazil for about two years and supported himself by teaching English, intervened, but the boy ran away. Witnesses said Martin was arguing with Oliveira when the officer fired three shots at the American. The officer would later allege he fired in self-defense after Martin tried to grab his weapon, but the prosecutor in the case, Viviane Tavares Henriques, said Martin "never went after the police officer's gun or in any way threatened him."

Critics contend that despite the recent changes, the police's culture of impunity remains intact.

"The logic of the police hasn't changed," said Alexandre Ciconello, a public security specialist at Amnesty International's Rio chapter, adding that changes in the way the statistics are compiled could be partly behind the downward trend. "It's still based on repression, on this idea of combatting an enemy, and executions and torture still remain part of the police's modus operandi."

Elizabeth Martin agreed that much remains to be done to root out impunity and corruption in Brazil's police force, and pointed to the 2010 acquittal of the officer who shot Joseph in a nine-hour-long trial that the Martin family alleged was riddled with anomalies. The officer was himself gunned down by unidentified assailants several months after the trial, according to news reports.

Since her nephew's killing, Martin has made the plight of a country thousands of miles away her personal cause. She quit her full-time job as a Harvard University director of administration to devote herself to her campaign. She's travelled to Rio and participated in meetings, conferences, marches and other demonstrations with groups representing the mothers of those killed by police, determined to use her nephew's death to make a difference.

Among the demands in an online petition she launched last month is giving officers in all 12 World Cup host cities training in low-lethal policing techniques.

"My goal is to get international pressure to get some real and lasting changes," Martin said. "I want to keep other families from having to go through what our family has been through."