Remember that mysterious sealed brown bag the defense gave the judge in June? It contains a15-inch stiletto knife, a source reportedly told ABC News. Observers have speculated that the knife could be the murder weapon, which police never found.GIRLFRIEND ON THE STAND? O.J.'s girlfriend, Paula Barbieri, has been subpoenaed to testify before the grand jury in an investigation of Al Cowlings, according to a CNN report. Cowlings is O.J.'s pal who drove him in a white Bronco with the LAPD hot on their tail. He may be charged with helping O.J. escape.