Judge Steven T. O’Neill, who is presiding over the case in Montgomery County, Pa., a suburb of Philadelphia, issued the ruling Friday allowing the testimony.
The ruling clears one of the last legal hurdles before trial, which is tentatively scheduled for June.
A hearing on another defense motion for a change of venue is set for Monday, according to Web site Pennlive.com.
Brian McMonagle, the 79-year-old comedian’s lead attorney, asked to move the trial because of the extensive publicity in Montgomery County.
Short of that, he wants a jury selected from another jurisdiction.
The case was cleared for trial a year ago in February, after O’Neill ruled that a prosecutor’s promise in 2005 not to prosecute Cosby was not binding on the current prosecutor.
Montgomery County (Pa) prosecutor Kevin Steele announced in Dec. 2015 that Cosby had been charged with one count of aggravated indecent assault, a felony.
O’Neill’s latest ruling fell short of Steele’s request to allow testimony from 13 other women who had accused Cosby of drugging and sexually assaulting them.
Steele argued in a hearing in December that the testimony would show a pattern of behavior on Cosby’s part that would erase any doubt that he didn’t understand “lack of consent” by unconscious or incapacitated accusers.
O’Neill said in a brief opinion that he is allowing one other woman to testify to balance the probative value of such testimony against possible prejudice against the defendant.