Unlike civilian grand juries, the military accused has substantial rights at an Article 32 hearing: the right to civilian and military appointed counsel, the right to be present, the right to examine available witnesses, the right to call available witnesses, and the right to present evidence that might persuade the investigating officer to recommend dismissal of charges or dispose of the charges through administrative vice criminal actions.
What should you do at the hearing
Except in extraordinary circumstances you should never waive an Article 32 hearing. You and your lawyer should take the opportunity to gather as much physical and documentary evidence as possible. You and your lawyer should cross examine as many of the witnesses as possible. This will be your first real opportunity to get witnesses on the record under oath; that means a real possibility of finding errors and inconsistencies in the investigation, the evidence, and the witness testimony.
Two exceptions to a non-waiver
There are two basic exceptions to the theory of never waiving an Article 32 hearing. (1) The prosecution is ill prepared and the investigation is flawed. In this situation an Article 32 hearing may put the prosecution on notice and allow them to prepare and further investigate. That opportunity to the prosecution may lead to a better case against you or additional and more serious charges. This is a fairly rare scenario. (2) You have been offered a very very good pretrial agreement (plea bargain) partly in exchange for waiving the Article 32 hearing. If you have a bad case, the prosecution has a strong case, and there is very little likelihood of getting a better deal in the future, this might be a valid strategy. On the other hand, there are many instances where the deal will get better later, or certainly not any worse.