"This is a horror, something that really doesn't even happen in the developed world," she said.
A spokesman for the Nutter administration said the mayor supports the idea and intends to appoint such a panel.
Winkler and Bryan held a news conference in the office of their lawyer, Robert J. Mongeluzzi, to announce they had filed suit Tuesday against developer Richard Basciano, the Salvation Army, and 17 other defendants involved in the ill-fated demolition project.
Their daughter, a 24-year-old artist, was one of six people crushed to death June 5 when an unsupported four-story brick wall of a building undergoing demolition fell on top of a Salvation Army thrift shop next door.
"Of course we're heartbroken. We miss her every day," said Bryan. "She was beautiful, vibrant, artistic, an intense personality, and we'll never have her now."
"There is nothing really I can say to capture the level of loss, a mother to lose her daughter," said Winkler.
Bryan, a structural engineer, continued: "Our grief has been made more difficult by the substantial evidence that the collapse was entirely avoidable, and in fact predicted."
He referred to correspondence between STB Properties, the owner of the building being razed, and the Salvation Army, warning months in advance about the danger the demolition posed to the thrift shop.
"We're bringing this litigation to find out what happened and who's responsible and make sure it never happens again," Bryan said.
The couple also urged public support for a proposal to turn the Salvation Army's property at 22d and Market Streets into a memorial park.
An Internet petition supporting the park's creation, at http://www.change.org/stopdemodeaths, had gathered 5,390 signatures as of Tuesday night, three weeks into the effort.
The lawsuit is the eighth filed by Mongeluzzi on behalf of victims of the building collapse.
"This lawsuit is one of the avenues of finding out what happened," Mongeluzzi told reporters. "They've told us, we want you to ask questions of anyone, to get to the facts of what occurred, what they knew, and when they knew it."
He said lawyers would likely take depositions from more than 100 witnesses. He said his firm intends to make the testimony publicly available - and, if necessary, would litigate with the defendants to do so.
"They [Winkler and Bryan] want nothing behind closed doors, zero. They want this in the public eye," Mongeluzzi said.
Winkler said she and her husband expected the case to lead to a public trial.
Mark McDonald, a spokesman for the Nutter administration, said the mayor had talked several times with Winkler and Bryan and intended to appoint an expert panel along the lines they suggested, "to do a thorough analysis of L&I."
"We are committed to it," McDonald said. "It's something the mayor and his senior team have been discussing for many weeks."
McDonald said the mayor also supports the concept of a memorial park at 22d and Market.
Both Winkler and Bryan fought back tears as they remembered their last moments with their daughter.
For Bryan, known as Jay, it was the night before her death, when he and his daughter cooked a birthday dinner for her brother, Chris, and watched Phillies outfielder John Mayberry Jr. hit a walk-off grand slam in the 11th inning to beat the Miami Marlins, 7-3.
Winkler was out of town at a conference that night, but returned to Philadelphia on a red-eye and walked into her home the next morning. Anne Bryan was leaving for a bicycle ride and talked her mother into joining her from Center City to Falls Bridge and back.
Back home, they ate Chris' birthday cake for breakfast and chatted about Anne's plans for the day.
"You think you're going to see the person at dinner," Winkler said. "She showed me these clothes she was going to donate to the Salvation Army. When +I heard the building collapsed, I knew she was probably there."
Operator's Hearing Delayed
Wednesday's preliminary hearing for Sean Benschop, the heavy-equipment operator charged with involuntary manslaughter and other offenses in the deadly collapse, was postponed to Dec. 10. His lawyer, Daine A. Grey Jr., said the postponement was "a strategic decision."
Benschop's request for a reduction in his $1.6 million bail was denied.
Contact Bob Warner at 215-854-5885 or firstname.lastname@example.org.