Circuit Judge Debra S. Nelson handed down her three-sentence ruling without explanation, the Orlando Sentinel reported Thursday.
In her first ruling on the defense request three weeks ago, Nelson said they had failed to show the information they sought from Benjamin Crump could not be obtained from other sources and that it was relevant to the case.
The attorneys wanted to question Crump about a woman who was on the phone with Martin just before he was fatally shot by Zimmerman and about an interview Crump later recorded with her.
Crump said the information was protected by attorney-client privilege.
Zimmerman, 29, is charged with second-degree murder in the February 2012 shooting death of the unarmed 17-year-old in the Orlando-area community of Sanford. Zimmerman maintains he acted in self-defense.