An indictment is an integral part of many judicial systems. It allows a person to be formally accused of a crime before they are placed on trial for it. An indictment allows a person time to prepare a defense. It also ensures that there is some evidence of guilt in the case. It was designed to prevent people from sitting in jail without a formal accusation of a crime and to ensure that specious allegations were not made.
Of course, the downside to an indictment is that it takes time. An indictment must be granted before a person can be detained. Sometimes this lapse in time allows a guilty person to escape. Officials must prove that a person could have plausibly been involved in the crime in order to obtain an indictment as well. While this was intended to protect the innocent, sometimes it allows the guilty to go free.