First Court Appearance
This is often an arraignment where the court formally informs you of the charges against you and your legal rights. In Colorado, officers are not required to appear at your arraignment and your case will not be dismissed for their failure to appear.
Subsequent Pretrial Conferences
Again, officers are not required to appear at these court dates.
Pretrial Motions Hearings
Officers are required to appear at this hearing. If motions to suppress evidence or motions to dismiss have been filed, judges may grant them by default if the officer does not appear. Of course, this is not automatic. Officers may have emergencies like anyone else. I have had officers not appear for these hearings because their wives were in labor and no judge will grant a motion to dismiss under these circumstances. Attorneys would look like jerks if they asked. However, if the prosecutor did not exercise "due diligence" in obtaining the presence of their critical witnesses, judges may dismiss under these circumstances.
Obviously, the officer is required to be present at this final stage. Again, exceptions occur but the prosecutor must establish that they exercised due diligence in obtaining the presence of their witnesses.