Hobson, who represents demolition contractor Griffin Campbell, said he expects prosecutors and the Nutter administration to challenge efforts to call them to testify.
But Hobson added that Nutter's e-mails involving the redevelopment and collapse were subpoenaed and surrendered to the investigating grand jury that recommended criminal charges against Campbell and heavy-equipment operator Sean Benschop.
Hobson said he was not implying that Nutter or top administration officials had done anything wrong. "We believe they are clearly relevant witnesses," he added.
In addition to the mayor, the suggested defense witnesses include Everett Gillison, Nutter's chief of staff and deputy mayor for public safety; Mary Stitt, chief of staff in the managing director's office; Alan Greenberger, the deputy mayor for economic development; and Carlton Williams, commissioner of the Department of Licenses and Inspections.
Hobson said Greenberger especially was involved in the planning of the project to transform the rundown strip of adult venues and commercial buildings to complement upscale investments such as the Murano, the 43-story luxury condominium tower at 21st and Market Streets.
Nutter press secretary Mark McDonald said the administration had not received a copy of the witness list and does not comment on pending litigation.
Campbell, 50, and Benschop, 43, are each charged with multiple counts of third-degree murder, conspiracy, and reckless endangerment. Both remain in prison without bail - Benschop has been locked up since shortly after the collapse - because convictions on more than one count of third-degree murder carry a mandatory life prison sentence.
Common Pleas Court Judge Benjamin Lerner did not rule on any issues in the case and Hobson said he would soon move to try the men separately. The judge set another hearing on Sept. 16.
Grey said that if the two are tried together, Benschop's defense would incriminate Campbell, who hired the excavator operator to take down the building next to a Salvation Army thrift store at 2136 Market St. It was during demolition that an unsupported four-story brick wall toppled onto the roof of the thrift store and crushed it.
Hobson said Benschop's statements to federal workplace safety investigators after the collapse were "clearly made against the best interests of my client."
Benschop and Campbell are the only two criminally charged in the collapse, although a Philadelphia grand jury is continuing to investigate and others could be charged.