Sure. The investigator can summarize findings, then provide either summaries of the testimony, or the actual interviews with names redacted, etc. Photos of Zimmerman's injuries and a description of the exact cause of Martin's death (bullet entry point); any other relevant forensic evidence, like powder burns on Martin's palm or palms, could also be made public without bringing charges. All at the investigator's discretion.
If there is a grand jury and a trial, grand jury testimony comes right in. The defendant is entitled to it, and so is the public.