CENTENNIAL, Colo. (Reuters) - A preliminary hearing on the merits of the criminal case against James Holmes, accused of indiscriminately firing upon patrons of a Colorado theater, was set for the second week of January by a judge during a brief court proceeding on Thursday.

The preliminary hearing, scheduled for the week of January 7 by Arapahoe County District Court Judge William Sylvester, will likely last several days.

It will mark the first time prosecutors will be able to lay out evidence they have amassed against Holmes and present their arguments for the case to proceed to a jury trial.

Holmes, a 24-year-old former neuroscience graduate student, is accused of opening fire inside a suburban Denver movie theater during a midnight screening of the Batman movie "The Dark Knight Rises" on July 20.

The rampage, one of the bloodiest acts of gun violence in the United States in recent years, killed 12 people and wounded 58.

Prosecutors have previously depicted Holmes as a young man whose once promising academic career was in tatters at the time of the shooting. He failed oral board exams for graduate school in June, and a professor suggested Holmes may not have been a good fit for his competitive doctorate program.

Holmes' lawyers, who analysts have suggested may be laying the groundwork for an insanity defense, have said Holmes suffers from mental illness and sought to get help before the shooting.

Holmes appeared in court on Thursday during the ten-minute hearing, handcuffed and shackled and growing a heavy but neatly trimmed beard.

(Writing by Mary Slosson; editing by Todd Eastham)