Earlier quoted context omitted.
Grand juries don't seem to correct the most egregious errors in either direction. Consider the famous assertion that a prosecutor can get a grand jury to indict a ham sandwich. On the other hand, consider the recent non-indictment of Darren Wilson. How often do grand juries defy the prosecutor's wishes? I certainly agree that a check on prosecutorial discretion is badly needed. But the grand jury system doesn't seem…
Aggregated statistics on grand juries are hard to come by, but let's use a random county for example: http://www.star-telegram.com/news/special-reports/article396... . Grand juries in Tarrant County, Texas declined to indict 11% of felony cases. Floating around the internet, you can find numbers ranging from 3-4% in New York counties to 5% in Texas as a whole. The high rate of indictments, of course, doesn't prove th…
Speaking from experience I can tell you that high-profile indictments are often discussed and decided before the indictment is presented, outside the juror's room.
And finally, we're having a little crisis currently in Harris county over the threatening of a witness by a grand jury foreman who was also a retired police officer, serving on a grand jury that was deciding to indict a man for the murder of another police officer.
http://www.texasmonthly.com/daily-post/grand-jury-system-tex...
http://www.texastribune.org/2014/09/15/time-ditch-key-man-gr...