PHILADELPHIA — The new district attorney in violence-weary Philadelphia had vowed not to get tough on crime but to get “smart on crime.” This month, R. Seth Williams began to make good on his word, downgrading penalties for possessing small amounts of marijuana from jail time to community service and fines.
It was an easy decision, said Mr. Williams, who took office in January promising changes that would reduce prosecutions but increase the conviction rate. Now he also spends hours each week visiting schools, exhorting students to graduate.
Philadelphia, after being battered for years by the worst sort of superlatives — the highest murder rate, the lowest conviction rate — seems ready to give Mr. Williams and his ideas a chance.
“This is like a breath of fresh air,” said Ellen Greenlee, chief of the city’s public defenders, who described the previous district attorney’s approach to charging suspects as “throw everything against the wall and see what sticks.”
Mr. Williams, the first black district attorney in the history of Pennsylvania, is a 10-year veteran of the office he is now shaking up. He looks younger than his 43 years and is happy for junior staff members to call him Seth.
In private and public appearances, Mr. Williams repeats practiced lines from a justice-reform movement that has taken hold in places like New York, San Diego and San Francisco and promotes, for lesser offenders, community courts and drug treatment rather than trial and prison.
“Crime prevention is more important than crime prosecution,” he said repeatedly last week as he rode from one event to another. “We need to be smarter on crime instead of just talking tough.”
“I’ve put my money where my mouth is,” he added in an interview, by redirecting his overstretched resources toward a more careful selection of cases and starting a computerized study of prosecutions to see why they so often fail.
But the real test of public support for Mr. Williams’s new directions, Ms. Greenlee and other legal experts said, may come if there is a surge in high-profile killings or the killing of a police officer by a repeat offender. Violent crime has fallen here in recent years, but of the 10 largest cities in 2009, Philadelphia still had the highest murder rate.
“We need to focus on the people who are shooting people,” Mr. Williams said of the newly lenient penalties for marijuana. Senior court officials said the shift would avoid 4,000 costly trials a year.
The only public condemnation came from Mr. Williams’s predecessor, Lynne M. Abraham, who during 18 years as district attorney sounded an increasingly hard line on crime. Ms. Abraham criticized the new marijuana policy, saying that “the drug cartels who import pot from Mexico are thrilled.”
While the drug shift caught the public eye, legal experts said the changes Mr. Williams was making, especially in the unit that decides what charges to file against those who are arrested, are far more important.
Previously, the charging unit included five lawyers, usually junior lawyers who were encouraged to file the widest and harshest charges they could, Mr. Williams said. Now the unit has 18 more experienced lawyers, who spend time considering what charges can realistically succeed. The office is also offering plea bargains earlier in the process, again to clear the courts for more serious cases.
“The new D.A. is one part of a sea change that is occurring in criminal justice in Philadelphia,” said Seamus P. McCaffery, a State Supreme Court justice.
The drive to streamline the justice system became easier, Mr. Williams and Justice McCaffery said, after an investigative series by The Philadelphia Inquirer last December found that the city had failed to obtain convictions in two-thirds of cases involving violent crimes, and that thousands of cases were dismissed because prosecutors were not prepared or witnesses did not appear.
Ms. Abraham, the former district attorney, who is now in private practice, called the articles misleading and said it was wrong to “do justice by the numbers.”
On one recent morning, Mr. Williams spoke to loud applause at the high school graduation at Freire Charter School.
“Why am I spending time here?” he asked. “Of the 75,000 people arrested each year for crimes in Philadelphia, what is the one thing they have in common? They didn’t graduate from high school.”
He described his own origins, saying they could easily have left him a street thug. When he was born in 1967, he went from the hospital to an orphanage; he does not know anything about his biological mother and said he was not interested in learning.
He spent time in two foster homes before being adopted, at 18 months old, by a middle-class black couple whom he credits with instilling a sense of civic duty. His father was a schoolteacher who also worked evenings at a recreation center, and his mother was a secretary.
As he congratulated the graduating seniors, he told them about a personal failure: He got into West Point, but had to leave in his first year when he failed math and chemistry.
He switched to Pennsylvania State University, where he was elected head of the Black Caucus and then the student government. He attended Georgetown Law School and started as an assistant district attorney under Ms. Abraham. Chafing at what he saw as a dysfunctional system, he resigned to run against her, unsuccessfully, in 2005.
The Philadelphia district attorney’s office was a stepping stone for the likes of Senator Arlen Specter and Gov. Edward G. Rendell, but Mr. Williams declined to speculate about his future.
Eugene J. Richardson Jr., one of the legendary Tuskegee airmen of World War II and a retired school principal, said he hoped the changes sought by Mr. Williams would pan out, adding, “So often the new broom comes in and then gets stuck in a corner.”