Robert J. "Joe" Halderman's attorney asked a Manhattan judge at a hearing to dismiss the attempted first-degree grand larceny charge.
Gerald Shargel said that Halderman was merely trying to sell Letterman a screenplay when he approached him with the package left in Letterman's car.
"There was no extortion. There was a screenplay for sale," Shargel said outside the courtroom. "There was a commercial transaction. Nothing more."
An attorney for Letterman called the host the victim in the case and derided Shargel's claim that Halderman was merely trying to sell a screenplay.
"It's classic blackmail, no matter how Mr. Halderman's lawyer wants to dress it up," Daniel Horwitz said.
Prosecutors have said Halderman left a bizarre and threatening package in Letterman's car on Sept. 9, demanding $2 million to keep quiet about some of the "Late Show" host's dalliances. The materials included a letter, a synopsis of a supposed screenplay that said Letterman's world would "collapse around him" when information about his private life was disclosed, photos, personal correspondence and portions of a diary, authorities said.
The diary entries were allegedly written by Halderman's former girlfriend and outlined her affair with Letterman.
Authorities then taped two conversations between Letterman's lawyer and Halderman -- including an exchange in which the lawyer gave Halderman a phony $2 million check, the Manhattan District Attorney's office said. Halderman was arrested after depositing it, prosecutors said.
The day before prosecutors unveiled the case last month, Letterman divulged it on his show, acknowledging he had had sex with women who worked for him.
Halderman, 51, a producer for CBS' "48 Hours Mystery," has pleaded not guilty. He could face five to 15 years in prison if convicted.