While "zone courts" would be a major change for Philadelphia, this prosecution model has been in place in Manhattan for decades.

When Robert M. Morgenthau was elected district attorney for the New York City borough in 1975, he changed the way cases were handled, assigning district attorneys to handle cases from start to finish.

As a result, the felony conviction rate increased dramatically, the office says. Morgenthau's successor, Cyrus R. Vance Jr., has maintained that structure since taking office this year.

Leroy Frazier, the executive assistant district attorney for Manhattan, said the system made for more effective prosecutions.

Putting one attorney in charge leads to better preparation, Frazier said.

The "vertical" approach allows prosecutors to adopt a courtroom strategy early on and quickly build a strong relationship with victims and witnesses.

"We feel that it is a positive for the D.A.'s Office," Frazier said.

Each of New York City's five boroughs is organized as a separate county, with its own district attorney.

Because of their high volume of cases and to control costs, most big cities follow the current Philadelphia "horizontal" model, under which different units of a district attorney's office pick up a case at each stage of the process.

Scott Burns, executive director of the National District Attorneys Association, in Alexandria, Va., said he favored a vertical method, if resources are available.

"I think everyone agrees vertical prosecution is the best model," he said. "In a perfect world, you have the case from beginning to end. It's more efficient that way."

He summed the approach up this way: "It's your case. You own it."

Federal prosecutors in Washington also pursue local criminal cases with a geography-based strategy. Teams of lawyers tackle cases in each of seven police districts.

At one time, the prosecutors in the Capitol even allocated murder cases to the local teams. In 2004, however, the U.S. attorney in Washington reversed that, again assigning homicides to an elite unit dedicated only to such crimes.

In Philadelphia, District Attorney Seth Williams has proposed to keep assigning homicide cases to the existing senior unit.