Former neighborhood watch volunteer George Zimmerman is questioning the expected use of a voice recognition expert at his murder trial next month.
Zimmerman's attorney filed a motion made public Monday asking for a hearing to determine whether testimony from a voice recognition expert would be allowed at trial.
Zimmerman is charged with second-degree murder for fatally shooting 17-year-old Trayvon Martin last year in a gated community in Sanford during a struggle. Zimmerman is pleading not guilty.
Neighbors called 911 during the struggle and cries of help can be heard on the calls. Martin's family claims the voice is that of the South Florida teen.
Zimmerman's father has said in court he believes the cries are from his son.
Zimmerman's attorney says jurors could be confused by an expert's testimony.