The argument was made in a letter from Witold "Vic" Walczak, legal director for the American Civil Liberties Union of Pennsylvania, who is representing 10 couples and a widow who want to overturn the state's Defense of Marriage act.
Attorneys for the state are seeking a variety of personal information from the plaintiffs, including details about any heterosexual relationships they have been involved in, the identity of those partners and the "natural parents" of any of their children, the Pittsburgh Post-Gazette reported Wednesday.
In his letter, Walczak told U.S. District judge John E. Jones "not only do these requests invade highly private and sensitive areas, none of them involved relevant information or are likely to lead to discovery of relevant information."
Tony Infanti, a law professor at the University of Pittsburgh, questioned the intent of the administration of Gov. Tom Corbett in asking for the information.
"At least with regard to the questions about past heterosexual activity, they [the state] might try to argue that this is evidence that sexual orientation is not so fundamental as they are claiming," Infanti said.
"It's really, obviously, none of their business," he continued. "Are they really going to put someone's sexual orientation on trial?"
On Tuesday, Jones denied the state permission to file an appeal with the 3rd U.S. Circuit Court of Appeals.
The case is set to go to trial in June 2014.