Grand juries are powerful tools for investigators to develop evidence and obtain testimony from reluctant witnesses that can help solve difficult crimes, both old and new. Edward Ohlbaum of Temple's Beasley School of Law says prosecutors sometimes use a grand jury to gauge public sentiment before filing charges in cases that are likely to be controversial, like shootings by police officers. He added that the grand jury process is also subject to criticism that it is one-sided, in that defense lawyers don't have the opportunity to present evidence or cross-examine witnesses.