Former District Attorney Lynne M. Abraham ripped into her successor's decision to treat some marijuana-possession cases more leniently, saying Monday that "local gangs and marijuana growers everywhere are positively overjoyed" at Seth Williams' new policy.

In a caustic statement made public at a U.S. Senate subcommittee hearing, Abraham also said, " 'Welcome to Philadelphia, Light Up a Joint' may just be our new slogan."

She said the new policy would give a pass to many serious lawbreakers.

"They are the same criminals who ruin the city's neighborhoods by aggressive, destructive conduct, engage in shoot-outs, commit violent crimes to support their habits, and they intimidate or kill witnesses," Abraham said.

Top aides to Williams immediately fired back. They said Abraham's "hyperbole" misrepresented the policy and gave a distorted description of defendants in such marijuana busts.

"I would see no evidence that the de minimus users of marijuana are significant contributors to this supposed Wild West violence," said Williams' top aide, First Deputy District Attorney Joseph McGettigan.

Abraham's criticism was directed at Williams' decision to relax how prosecutors treat people arrested in Philadelphia for possession of small amounts of marijuana for personal use.

Under the policy shift, announced by Williams last month, prosecutors will charge such cases as summary offenses rather than as misdemeanors. People arrested with up to 30 grams of the drug - slightly more than an ounce - may have to pay a fine but will face no risk of a criminal record.

Williams has said he was not decriminalizing marijuana use, but trying to be smarter in fighting crime.

While the new policy liberalizes how prosecutors treat marijuana cases, offenders have not been treated harshly for years, rarely serving prison time. That includes during Abraham's 18-year tenure, which ended in January.

Pennsylvania law mandates only a maximum prison term of 30 days for the crime of possessing marijuana for personal use.

Williams initially said he would make the change by the end of April. On Monday, his staff said the shift had been delayed by problems reprogramming court computers to carry out the new policy. It will now be put into effect in early June, they said.

The District Attorney's Office has concluded that state marijuana law allows it to impose the shift unilaterally, without changes in either state or local law, the staff said.

Williams has said his aim is to divert 3,000 small-time marijuana cases annually out of the main court system, freeing prosecutors and judges to devote time to more serious crimes. The diverted cases amount to 5 percent of the caseload in criminal court.

"We can't declare a war on drugs by going after the kid who's smoking a joint on 55th Street," Williams said last month.

Abraham suggested in her statement that Williams had misunderstood the threat posed by those busted for marijuana possession.

"These people arrested for 20 to 30 grams of pot are not first-time offenders for the most part," she said. "They frequently are the repeat offenders who have committed untold numbers of crimes and have been arrested dozens of times."

The new policy toward marijuana was developed in consultation with Chief Justice Ronald D. Castille of the Pennsylvania Supreme Court and fellow Justice Seamus McCaffery. Castille is a former Philadelphia district attorney and McCaffery a former Philadelphia police detective.

In her statement, Abraham said Williams and the two justices "have, effectively, legalized marijuana without legislative enactment."

"The marijuana market is into the billions. Now we are going to encourage its growth."

"Just think of all those [Customs] officers on the U.S.-Mexico border trying to stem the tide of marijuana mules, who now will be welcomed to bring their product into Philadelphia."

Abraham said that local gangs and marijuana growers would welcome the new policy and that "the drug cartels who import pot from Mexico are thrilled."

Chris Goldstein, a leader of the Philadelphia chapter of the National Organization for the Reform of Marijuana Laws (NORML), said he was stunned by Abraham's comments.

"This is a joke," he said. "It's like a fusillade of falsehoods here."

He said that most marijuana was domestically grown and that most smokers posed no threat to anyone.

"This is a false characterization of the marijuana users of Philadelphia," Goldstein said. "The vast majority of the marijuana smokers are law-abiding citizens who are working every day to contribute to this city."

Abraham and Williams have had a tense relationship since Williams put a spotlight on the low conviction rate in the District Attorney's Office when he sought to unseat Abraham in the 2005 Democratic primary. Abraham turned aside that challenge but chose not to stand for reelection last year.

Since taking office in January, Williams has dramatically shaken up the office and taken steps that have implicitly criticized Abraham's tenure, such as overhauling the Charging Unit.

Williams has said police will still arrest and handcuff marijuana suspects, who would be held in custody while they are fingerprinted and photographed.

Abraham said the shift might provoke a class-action suit from the defense bar, contending that it was improper for police to take suspects into custody for mere summary offenses, such as citations for littering.

Law-enforcement officials in other cities and states have taken steps toward decriminalization or something approaching it. Several dozen cities have enacted "lowest law-enforcement priority" ordinances, stipulating that police pursue such cases as a last resort.

Voters in Seattle approved a ballot question mandating such a change in 2003. Since then, arrests for possessing small amounts of marijuana have fallen by three-quarters. In 2005, Denver voters approved a measure legalizing possession of less than an ounce, or 28 grams. San Francisco passed a similar law in 2006.

Several states also have taken a softer stance on marijuana possession. Massachusetts decriminalized marijuana in 2008, making it a civil offense and imposing a $100 fine for possession of less than an ounce.