CENTENNIAL — After a day spent hunting fruitlessly for the “law enforcement source” who leaked information to a national news organization about the Aurora theater shooting, attorneys for suspect James Holmes said Monday afternoon they intend to subpoena the reporter who wrote the story.

The move opens a complicated new legal front in the case even as attorneys are preparing for the case’s most important hearing to date — a preliminary hearing scheduled to begin Jan. 7 at which investigators are expected to reveal never-before-told details about the July 20 shootings that killed 12 and injured at least 58 at the Century Aurora 16 theater.

Laws shield reporters from having to reveal sources; overcoming those laws to put reporters on the witness stand typically involves a courtroom battle. Prosecutor Rich Orman said he expected the extended fight over the leak to add extra delay to a case that has already stretched five months with no trial date in sight.

Even defense attorney Daniel King acknowledged the outcome of the leak battle is uncertain.

“It appears to me,” King said Monday afternoon, at the conclusion of a four-hour hearing in which 14 law-enforcement officers testified and none said he or she had talked to the media about the Holmes case, “we are going to be executing an out-of-state subpoena — or attempting to do so.”

The subject of the leak was a notebook Holmes mailed to his psychiatrist at the University of Colorado.

Two days after the notebook was found stuffed with burnt money in a white bubble-mailer inside a CU mailroom, FoxNews.com’s Jana Winter reported that the notebook contained violent writings and drawings. Holmes’ name was handwritten on the return-address line, Winter reported then and officers confirmed Monday.

“Inside the package was a notebook full of details about how he was going to kill people,” a law-enforcement source told Winter.

Holmes’ attorneys contend the disclosure violated the judge’s gag order, and they want the judge to punish the prosecution for the breach.

A Fox News spokeswoman said Monday that the news organization would evaluate the promised subpoena once it is received.

As testimony Monday showed, a number of investigators handled the notebook. Four — CU-Denver Police Chief Doug Abraham, Aurora police detectives Alton Reed and Matt Fyles and an Adams County bomb-squad officer — said they touched it at various points. Five in total said they saw inside the notebook, most notably when Reed fanned the pages while preparing a search warrant to seize the notebook.

But none of the officers admitted to getting a good look at what was on its pages.

No officer admitted to speaking with the media.

Left without answers to their queries, defense attorneys used the occasion to raise questions about investigators’ handling of the notebook. Reed, for instance, was asked why he chose to flip through the notebook even though the defense had already asserted it should be off-limits to police.

“My intention was to separate the (burnt) currency from the notebook, so we could handle it separately,” he said.

The hearing marked Holmes’ first appearance since he was taken to a hospital last month after ramming his head into a cell wall at the Arapahoe County jail, an event that forced the postponement of a previous hearing. In court, he showed no sign of injury.

The next hearing in the case is scheduled for Jan. 2, when both sides will confirm whether they are ready to proceed to the preliminary hearing the following week.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold