WHEN Cory Booker was elected mayor of the New Jersey city of Newark last year, he understood better than most the problems of poverty and violent crime that were returning to haunt many of America’s middle-sized cities.

Booker became the first African-American mayor of Newark to live in a near-derelict flat in a low-income housing project. He had no heating and, although he was later forced to move when his building was demolished, he chose a new home amid the abandoned houses of Hawthorne Avenue, one of the city’s grimmest streets.

The 37-year-old mayor explained that he wanted to be part of the community he led, and that his presence at the rotten heart of New Jersey’s biggest and most violent city might help to inspire an urban revival.

It has proved tougher than he thought. When city police tallied their crime statistics for 2006, they found that the number of murders had risen for the fourth straight year to a new record of 106 - ranking Newark among America’s most dangerous cities. There were 12 more killings in the first five weeks of this year.

The only consolation for Booker was that he is far from alone in grappling with a wave of violent crime that has confounded trends of the past decade and shaken police departments across America.

After years of falling murder rates, widely attributed to radical changes in police techniques, violent crime has rebounded sharply, according to a new study by a leading police research group.

New York and Los Angeles, which for years have recorded big falls in homicides, have seen a reversal of the trend. Other cities that recorded a 20% or more increase in murders in 2004-6 included Baltimore, Detroit, Memphis, Newark, Philadelphia, San Antonio and Seattle. Cincinnati had a record 89 murders last year, up from 79 in 2005.

Murders in New York climbed from 540 in 2005 to 590 last year, although officials attribute much of that increase to an unusual number of victims who died in 2006 after failing to recover from assaults the year before.

The statistics amount to “the makings of an epidemic”, according to Chuck Wexler of the Police Executive Research Forum, which released the new report. Its findings have prompted an angry debate about why murders are rising after many years when police claimed to be winning the war on violent crime.

In many cities, police have blamed both an increasing availability of guns and a lethal tendency among black youths to use them in even petty disputes. Criminologists and other experts have criticised police for failing to treat black-on-black violence seriously – in effect, standing back while gang members slaughter each other.

President George W Bush’s administration has also been accused of diverting billions of dollars from police budgets to pay for antiterrorist measures. “They have put homeland security before home-town security,” said one leading law professor.

Booker still hopes that his commitment to Newark’s economic rebirth will turn the tide of violence. But he was so short of funds for a new antigun initiative that he was forced to raise the money privately from business leaders.

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