Unless a defendant is charged by way of a grand jury indictment he or she is entitled to a Preliminary Hearing. At a Preliminary Hearing a judge determines whether there is sufficient evidence against a defendant to justify going to trial. It is often called a probable cause hearing. Officers must testify to evidence and be subject to cross examination by the defendant.
Before Proposition 115 was passed several years ago, a Preliminary Hearing was thought to be a critical stage of the proceedings. It was a time when the defense could challenge the evidence and have a "free shot" at the witnesses on cross examination. The law has changed and how a criminal defense lawyer represents his clients has to change with it.
In deciding whether or not to conduct a Preliminary Hearing, a defendant needs to think about what he want to get out of it. For example, if a defendant wants to question the police officer about descriptions given by a witness he would not waive Preliminary Hearing. If a defendant wants to present an affirmative defense at the Preliminary Hearing in order to try and prove his innocence, a Preliminary Hearing is required.
The problem with the Preliminary Hearing is that the standard of proof for the prosecutor is the low level of reasonable suspicion that the defendant committed the crime, that even if the judge thought the defendant was not guilty he still would hold the defendant to answer for trial. The issue for the judge isn't that the case is weak or the defendant won't be proven guilty at trial. The standard is only, is the suspicion there? The District Attorney does not have to put on all his evidence at the Preliminary Hearing so the judge will normally ignore the fact that the standard has been barely met. He can even comment that if he had to decide guilty or not guilty he would vote not guilty. That is little comfort to a defendant heading for a jury trial.
Waiving or giving up the right to have a Preliminary Hearing is acceptable if the police officer is simply going to recite what is in his report, because it is not going to be helpful to the defendant. However, there is a danger to the defendant in conducting a Preliminary Hearing, and a good defense attorney needs to consider the consequence that the District Attorney can charge a defendant with new counts if he has proven them at the Preliminary Hearing. That is why a defendant can start a Preliminary Hearing being charged with only one count and end up afterwards with many more counts.
Whether a defendant conducts a Preliminary Hearing is a tactical decision. A lawyer needs to think and analyze the reasons for doing a Preliminary Hearing and not just blindly conduct one. There isn't one sure way to defend a felony charge. But, one thing IS sure, a smart lawyer thinks about what he is doing and doesn't do anything without considering the risks and benefits. That is especially true when considering whether to waive a Preliminary Hearing or not.