Source : Washington attorney issued grand jury subpoena for school hard drives . Forensic body was found in a rolled-up gym mat in now . Previously released video was missing footage from high school gym . CNN 's Devon Sayers contributed to this report , which was written by Eliott C. McLaughlin . Kendrick Johnson 's video analyst : Hard drives may have been overwritten by January .
Source : Washington attorney issued grand jury subpoena for school hard drives . Forensic body was found in a rolled-up gym mat in now . Previously released video was missing footage from high school gym . Kendrick Johnson 's video analyst : Hard drives may have been overwritten by January .