The court papers say a detective "fanned" through the notebook, The Denver Post reported. Prosecutors have said they haven't seen the notebook and don't know what is in it.
Holmes was arrested at a theater in Aurora, Colo., where he allegedly killed 12 people and wounded more than 50 others. The shooting spree occurred during a midnight premiere showing of "The Dark Knight Rises."
The notebook, sent by mail to a psychiatrist who had treated Holmes, was found in a mailroom at the University of Colorado a few days after the killings. Court documents said the package was examined by X-ray and then opened by bomb squad technicians.
After the detective examined it, it was sealed.