Prosecutors will be allowed to call an expert to testify about why dozens of people felt that they couldn't leave a sweat lodge ceremony that turned deadly.
Yavapai County Superior Court Judge Warren Darrow made the ruling Monday, a day before opening statements begin in James Arthur Ray's manslaughter case.
Darrow says Rick Ross can testify about large group awareness as long as prosecutors provide an appropriate foundation.
The judge says defense attorneys can cross-examine Ross on his cult deprogramming practices but not bring up his criminal history.
Darrow also is allowing prosecutors to play parts of an audio recording of Ray's October 2009 "Spiritual Warrior" event that culminated with the sweat lodge ceremony.
Three people who were among the more than 50 in the heated enclosure died.
Ray has pleaded not guilty.