"I'm here to say, 'Not so fast," Shargel said. "I look forward to cross-examining David Letterman, because I don't think the full story is before the public. There's much more to this story." Freed on $200,000 bail, Halderman faces up to 15 years in state prison if convicted.
Last week, Letterman revealed to the studio audience that he'd received a package three weeks ago containing a threat to reveal those indiscretions if he didn't pay up.
In a press conference last week before Halderman's arraignment, Manhattan District Attorney Robert Morgenthau said Halderman demanded to be paid $2 million in an initial meeting with Letterman Sept. 9, when Halderman allegedly waited outside Letterman's New York City apartment.
Halderman had threatened to reveal "personal and private information" if Letterman did not accede to his demand to purchase a one-page screenplay he presented at the initial meeting, said Morgenthau.
The district attorney said the screenplay described a scenario in which Letterman's world would "collapse all around him" and would lead to a "ruined reputation."
Three subsequent meetings between Letterman and Halderman were recorded by Letterman's attorney, Morgenthau said.
Shargel told "Good Morning America" that he had not yet had a chance to hear the tapes that prosecutors say prove his client tried to extort Letterman, nor read the transcripts.
And while Shargel admitted that Halderman did attempt to cash Letterman's phony $2 million check, "the surrounding circumstances are what's relevant," Shargel said.
ABC News' Eileen Murphy, Michael James, Lindsay Goldwert, Brandon Bodow and Richard Esposito contributed to this report.