Typically, the attorney general represents the state in cases involving a state constitutional challenge, but Attorney General Kathleen Kane announced in July she would not do so following the U.S. Supreme Court ruling overturning the Defense of Marriage Act.
Corbett's general counsel, James Schultz, said the "unique circumstances" of this case compelled the Office of General Counsel to retain expert assistance in this case.
"The Office of General Counsel provides comprehensive legal services to numerous state agencies and executives, but we do not typically defend cases that solely challenge the constitutionality of a statute," Schultz said. "Who better than a former Supreme Court justice and his firm to assist in addressing this type of fundamental question?"
Lamb said in a statement that he looked forward to having the opportunity to serve the commonwealth again and "offering our insights to this serious constitutional question."
Lamb will be paid $400 an hour for his legal counsel work, while others in his firm will receive $325 an hour for their services.
The news release issued by Corbett's office noted Lamb's "history of bipartisan service to the commonwealth."
He was nominated to an interim one-year appointment on the Pennsylvania Supreme Court in January 2003 by then-Gov. Mark S. Schweiker. He was approved by incoming Gov. Ed Rendell and confirmed by the GOP-controlled Senate.
Lamb also served as district attorney for Chester County from 1972 to 1980.
Witold Walczak, the legal director for the American Civil Liberties Union of Pennsylvania, who is representing the plaintiffs, said he appreciated having "good counsel" on the opposing side.
"Generally it improves presentation of the competing arguments, which helps the judge reach a sound decision," he said.
A case management conference is scheduled for Sept. 30 before U.S. District Judge John E. Jones 3d, at which time a trial date would likely be set, Walczak said.
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