A ruling released Thursday doesn't identify the witnesses by name. It describes them as "lay witnesses" who don't want to be interviewed by defense investigators.
The suspect, James Holmes, is charged with killing 12 people and wounding 70 in a movie theater in July. He faces multiple counts of murder and attempted murder. His lawyers have said he is mentally ill.
Next week's hearing is for the judge to determine whether prosecutors have sufficient evidence to warrant a trial.
Prosecutors asked the judge to quash the defense subpoenas, arguing the defense has no right to call the witnesses. The judge disagreed.