Mayor Nutter, Police Commissioner Charles H. Ramsey, and District Attorney Seth Williams say the reduction reflects a sustained commitment to a crime-fighting plan that combined data-driven law enforcement and old-school, shoe-leather police work. The plan targets gun criminals and the most violent neighborhood "hot spots."
Williams and other officials say the fall in deadly violence also reflects reforms in the Philadelphia courts. The state Supreme Court has shaken up the city system to make sure more cases go to trial.
"Anyone who tells you it's one thing doesn't know what they're talking about," Nutter said in an interview last week. The key, he added, was "a consistent, regular focus" on a strategy.
As of Saturday, the homicide total was 238 - vs. 319 at the same date last year.
If the final homicide tally hits 250, that would be the fewest since 1967, when 234 were killed.
The drop this year is part of a downward trend in homicide in most big cities across the nation, statistics show.
The overall decline in crime in Philadelphia has been across the board. Both violent and nonviolent offenses are down for the year. Shootings are down 15 percent.
Nutter said the dramatic reduction in crime, coupled with the recent uptick in city population, "all helps to tell the resurgent story of the city."
Nutter said the decline is a big step toward a pledge he made in his first inaugural address five years ago - a promise to cut the homicide rate by as much as half. He said he asked Ramsey, the police chief he appointed when he took office in 2008, to develop a multifaceted plan.
Other factors may be at work, too.
According to figures from the Pennsylvania Trauma Systems Foundation, Philadelphia emergency-room doctors seem to be saving more lives this year.
In 2012, nearly 28 percent of gunshot victims died in the hospital. This year, the most recent figures suggest, only 20 percent have succumbed.
The gray Mercury Grand Marquis with its back window shot out swerved onto Broad Street, drifting through afternoon traffic as it crashed into the side of a car parked outside the 35th Police District in Ogontz.
From the driver's-side door of the car tumbled a 23-year-old man with a bullet wound in his side. He had been trying to get to Einstein Medical Center off Broad Street on Wednesday, but, fading, he made it only as far as the 35th.
After rushing outside alongside his officers, Capt. Joseph Fredericksdorf, the district's commander, knelt beside the wounded man.
He had been shot, the man told the captain, on nearby Smedley Street.
While he survived, his startling arrival was a reminder that shootings are commonplace in parts of Philadelphia, like the 35th.
Still, killings have dropped dramatically in the district this year - and all across the Police Department's Northwest Division.
Compared with last year, homicides are down 43 percent in Northwest Division, from 72 deaths to 41, Deputy Police Commissioner Kevin Bethel said.
That decrease represents the biggest drop citywide among all six police divisions.
On the walls of his office at the 35th District, Inspector James J. Kelly 3d, commander of the Northwest Division, has maps of the four districts that make up his command.
In each of his maps are shaded green areas that represent targeted hot spots - the high-crime areas that Commissioner Ramsey tasked all commanders to identify late last year.
"We made full-press efforts in those areas," Kelly said.
Using crime mapping systems that break down crime by time and place, Fredericksdorf assigned two-person teams to each problem corner within the key areas.
"They adopt those corners," Kelly said.
To show how the department drills down, Fredericksdorf pulled out an intelligence dossier previously assembled about the block where the man in the Marquis had been shot only minutes before.
"It's page after page of the guys who hang out over there," he said.
Last December, Ramsey shook up the leadership of much of the department, installing new commanders at police headquarters and appointing new captains in many busy districts, including Fredericksdorf.
Ramsey said he has demanded that the captains of the 21 police districts develop sophisticated strategies for their turfs - and insist on results.
Street-level officers, in turn, are now expected to buy in.
"They are taking ownership," Ramsey said. "When they feel part of their community and they feel embarrassed when crimes are occurring in their areas, that's when you know it's clicking."
As police have executed the strategy, they have begun to break the cycle of retaliation and vendettas that has fueled violence. Academic experts say this can accelerate a drop in crime.
City Prosecutor Edward McCann, Williams' top deputy, said police and prosecutors have welcomed input from academic researchers to deepen their understanding of city crime data. He said the next step would be to engage university experts to figure out what precisely has driven down crime.
"The question is, are we building something that is sustainable?" McCann asked. "It will be helpful for us to have an objective look at the numbers to see what is working."
Last week, 33 young men from South Philadelphia sat in a City Hall courtroom, looking surly and bored as they faced a phalanx of top law enforcement officials and community activists.
The young men all had arrest sheets.
Through intelligence, police and prosecutors had identified the men as at risk of killing or being killed.
"Take this message back to your neighborhood and your crew," District Attorney Williams told them. "We will hold every member of your group responsible, no matter who pulls the trigger or why. You understand that?"
After Williams, the group heard from the mother of an 18-year-old who was shot dead in a case of mistaken identity in 2011.
Movita Johnson spoke of how she kissed her son Charles goodbye as he lay dead in the hospital.
"Please save yourselves," she pleaded with the group.
The "call-in" was part of a new program police and prosecutors call "Focused Deterrence." Borrowed from Boston, the project has begun to quell gun and gang violence in South Philadelphia.
To build the effort, authorities pooled intelligence to identify 600 "impact players" - triggermen, major dealers, robbery teams - and prioritized them for enforcement, as well as social services.
While crew members are offered job training and other alternatives to street life, if one member shoots, as Williams warned, the entire crew suffers: probation-violation hearings, stepped-up drug testing, higher bails, stiffer sentences, even crackdowns on unpaid utility bills.
It appears to be working.
While violent crime is down across the city, the numbers in South Philadelphia stand out.
Compared with last year, homicides are down 47 percent - from 34 to 18 - and shootings fell 24 percent, from 92 to 70.
The program is the latest in a series of initiatives pushed by Williams since he became district attorney in 2010. Among other reforms, he has reorganized his office so that prosecutors work cases by the neighborhood in which crimes occur. The idea is that prosecutors would immerse themselves in the community, identifying the worst offenders and building alliances with police and civic groups.
Picking up on a program from St. Louis, Williams also launched GunStat, a joint project with police to identify and lock up the most serious gun offenders.
Under the program, defendants facing gun charges in the city have been given dramatically higher bail - in many cases tenfold higher.
A year ago, a typical defendant charged with possession of an illegal handgun - not with shooting it - would have had to post $1,500 to get out of jail. For those charges now, defendants can expect to pay $5,000 to $25,000, according to statistics from the District Attorney's Office.
Williams said the courts had cracked down, too, responding in part to a 2009 Inquirer series that reported Philadelphia had one of the lowest conviction rates for violent crimes in the nation.
By the end of the meeting in City Hall last week, many in group had become more attentive. Williams told the group that prosecutors wanted to help them, not hurt them.
"I don't want to put you in jail," Williams said. "I don't want to see you dead."
Nutter promised continued pressure next year.
"When you set a new low, the question is how do you drive that now," the mayor said.
History may be on his side. Since 1970, each time homicides dropped sharply in any one year, the number killed invariably fell again the following year.
Ramsey agreed with the mayor and set his sights on an ambitious goal.
"I firmly believe we can go back below 200 murders in this city," he said, referring to an annual death toll last registered in 1966. "We are already looking at the lowest number since 1967, so it's not out of reach."