CENTENNIAL, Colo. -- CENTENNIAL, Colo. (AP) — The defendant in the Colorado movie theater shooting had the day of the attack marked "with a unique symbol" on a calendar, a Batman mask and a violent drawing in his apartment, according to testimony Wednesday.

The discoveries were revealed during a pretrial hearing on whether evidence seized from the apartment after the shooting can be introduced at James Holmes' trial.

There was no testimony regarding the significance of the items. "The Dark Knight Rises," the most recent Batman movie, was showing as 12 people were killed and 70 others were wounded in the July 2012 massacre.

Holmes' attorneys have acknowledged their client was the gunman, but he has pleaded not guilty by reason of insanity to murder and related charges.

Prosecutors are seeking the death penalty and will have to prove he was sane during the attack.

Most of the evidence being contested during the hearings this month could be used by prosecutors in an attempt to undermine Holmes' insanity plea.

FBI agent Leslie Kopper testified that a bureau-led evidence team found the mask and a calendar with July 20, 2012, marked "with a unique symbol," which she didn't describe.

Kopper didn't elaborate on the discoveries, and neither prosecutors nor defense lawyers asked further questions about them.

Aurora police Detective Thomas Wilson testified that he found the violent drawing in a spiral notebook inside a backpack, saying it was "some kind of maze game involving a serial killer."

Attorneys did not ask him follow-up questions.

Holmes also sent a notebook containing violent drawings to a psychiatrist before the shootings, according to Fox News reports.

Other evidence to emerge during pretrial hearings includes statements Holmes made after his arrest and computer and bank records that police have said document his purchases of weapons and explosives.

The judge has not said when he will rule.

The defense argues the evidence from Holmes' apartment should be thrown out because police began their search before they had a warrant.

Prosecutors say the search was legal because Holmes had told them he had explosives at his apartment, and they didn't have time to wait for a warrant because of the potential danger.

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  • James E. Holmes

    James E. Holmes, left, appears in Arapahoe County District Court, with defense attorney Tamara Brady, right, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting on Friday, July 20, in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes, Tamara Brady

    People in the courtroom listen to the court hearing of James E. Holmes in Arapahoe County District Court Monday, July 23, 2012, in Centennial, Colo. Holmes is accused of killing 12 and wounding 58 in a shooting rampage in a Colorado theater on Friday, July 20. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    James E. Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • In this image taken from video provided by KUSA.com, James Holmes, left, the suspected gunman in Friday's Colorado theater massacre, makes his first appearance in court with his attorney Tamara Brady in Centennial, Colo. on Monday, July 23, 2012. (AP Photo/KUSA.com)

  • Carol Chambers

    Carol Chambers, district attorney for the 18th Judicial District, speaks during a media availability after a court appearance by James Holmes at the Arapahoe County Courthouse, Monday, July 23, 2012, in Centennial, Colo. Twelve people were killed and dozens were injured in a shooting attack early Friday at a packed theater during a showing of the Batman movie, "The Dark Knight Rises." Police have identified the suspected shooter as Holmes, 24. (AP Photo/Alex Brandon)

  • James E. Holmes, Tamara Brady

    James E. Holmes, center, appears in Arapahoe County District Court, with public defenders Tamara Brady, right, and Daniel King Monday, July 23, 2012, in Centennial, Colo. Holmes is accused of killing 12 and wounding 58 in a shooting rampage in a movie theater on Friday, July 20 in Aurora, Colo. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    James E. Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting Friday, July 20, in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • David Sanchez

    David Sanchez, whose son-in-law was critically wounded, speaks after a court appearance by shooting suspect James Holmes at the Arapahoe County Courthouse, Monday, July 23, 2012, in Centennial, Colo. Twelve people were killed and dozens were injured in the shooting attack early Friday at an Aurora, Colo., theater during a showing of the Batman movie, "The Dark Knight Rises." (AP Photo/Alex Brandon)

  • Family members of a victim from last week's theater shooting in Aurora, Colo., link hands as they arrive for a court appearance by shooting suspect James Holmes at the Arapahoe County Courthouse, Monday, July 23, 2012, in Centennial, Colo. Twelve people were killed and dozens were injured in the shooting attack early Friday at the packed theater during a showing of the Batman movie, "The Dark Knight Rises." (AP Photo/Alex Brandon)

  • A woman, third from left, is led to the courtroom where James Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is the suspect in the mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Barry Gutierrez)

  • Anggiat Situmeang,

    Anggiat Situmeang, center, who suffered an injury in last week's theater shooting in Aurora, Colo., is helped inside to see a court appearance by alleged shooter James Holmes, at the Arapahoe County Courthouse Monday, July 23, 2012, in Centennial, Colo. (AP Photo/Alex Brandon)

  • James E. Holmes

    Assistant District attorney Karen Pearson speaks at a hearing for James E. Holmes in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    James E. Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    James E. Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    James E. Holmes, left, appears in Arapahoe County District Court, with defense attorney Tamara Brady, right, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting on Friday, July 20, in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)

  • James E. Holmes

    District Court Judge William Blair Sylvester speaks as James E. Holmes appears in Arapahoe County District Court, Monday, July 23, 2012, in Centennial, Colo. Holmes is being held on suspicion of first-degree murder, and could also face additional counts of aggravated assault and weapons violations stemming from a mass shooting last Friday in a movie theater in Aurora, Colo., that killed 12 and injured dozens of others. (AP Photo/Denver Post, RJ Sangosti, Pool)