In a grand jury presentment, the standards of evidence are relaxed, and there are no defense attorneys to advocate for the accused. This means that prosecutors can, and often do, stack the evidence in favor of their case in order to ensure an indictment -- often excluding details that would support the case for the accused.
In the Ferguson case, however, it doesn't appear the prosecutor is holding anything back. By all accounts, McCulloch has presented a bulk of the evidence, such as having the medical examiner hired by the Brown family testify -- likely more than would ever be allowed in jury trial. Some have expressed concern regarding whether this is proper.
Is McCulloch weakening his case by presenting so much of the evidence? He is a man with a law enforcement background, a man sympathetic to cops, a man whose own father was shot and killed by a black man.
Would McCulloch intentionally sabotage his case to avoid charges for Wilson?