Preliminary hearings are generally associated with felony charges and do not occur in all instances. Additionally, in some states, grand jury systems are used in place of preliminary hearings. Both grand juries and preliminary hearings, however, exist for the purpose of allowing a jury or judge – the latter in the case of preliminary hearings – to determine whether sufficient evidence exists to justify the more expensive and protracted process of a criminal trial. In short, preliminary hearings are a cost- and time-saving measure used to ensure that a criminal trial is indeed warranted on the basis of the prosecution’s accumulation of evidence.
The advantages of a preliminary hearing, then, are mainly financial and scheduling in nature. If a preliminary hearing results in a determination by the presiding judge that insufficient evidence or probable cause exists to justify the time and expense of a full trial – and most major cities perennially face backlogs of criminal cases waiting to be tried – then the criminal justice system is spared the financial costs associated with a trial, especially when a jury is involved and the risk exists that the jury may have to be sequestered at government expense for the duration of the trial. A more important consideration or advantage of a preliminary hearing, at least for the prosecution, is that the “probable cause” standard is relatively easy for prosecutors to meet relative to the “beyond a reasonable doubt” standard that will occur in a criminal trial. For the defense council, the advantages of a preliminary hearing reside primarily in the exposure it provides for the defense of much of the prosecution’s case. In other words, the evidence and witness statements that form the basis of a preliminary hearing are now a matter of public record available to the defense at an earlier opportunity than would otherwise be the case, thereby providing more time to counter those statements or to challenge the validity of the evidence.
The disadvantages to a preliminary hearing are mainly on the prosecution’s side, but also exist for the defense. A determination by the judge that probable cause exists to proceed with a criminal trial is bad for the defense because it taints the defendant with the brush of guilt despite the lower standard of proof required of the prosecution at such a hearing. While any jury selected at a subsequent trial will presumably be ignorant of the details of the preliminary hearing, the fact of the preliminary hearing is sufficient to color perspectives. The disadvantage for the prosecution, as noted above, is the revelation of at least some of its evidence before the defense, which now has greater advance notice of that evidence and can consequently seek ways to have that evidence barred from admission in the trial, for example, on grounds of unconstitutional search and seizure.