This is a very solemn oath (for some witnesses) and a very noble goal. But, I think that it is, at least partly, a sham. Do we actually expect that a witness is going to tell the whole truth in their testimony? We do not. And our system assumes as much.
If we really wanted a witness to give us the whole truth, then the rules of evidence would require that a witness tell the court everything that they know about an event or factual issue without being prompted by a question. In fact, the judge would just instruct the witness something along the line of “Mr. Jones, we are here to deal with the accident that occurred on May 1st, 2009 between the Plaintiff and the Defendant. Please tell the jury everything that you can remember about that accident.”
Instead, we rely on the attorneys to elicit information from witnesses. And anybody who has taken a trial advocacy course in law school knows that the whole aim of examining a witness is to elicit the information that you want in evidence and avoid the information that you do not want in evidence. Witness examination is not about discovering the whole truth; it is about getting the part of the truth that you want the jury to hear into evidence. As we are taught from the beginning, it’s the other attorney’s job to bring out the “whole” truth.
In theory, the adversarial system and cross-examination should ensure that all of the relevant facts are brought to light. But, that’s only in theory. And that places the task of eliciting all relevant evidence on the attorneys, who are (and are required to be) biased towards their client. If the whole truth were really the goal, we would require attorneys to inquire about facts that are injurious to their client’s cases, not just the “good” facts. Or, perhaps there would be an objective court appointed attorney to inquire as the “whole truth” before the attorneys for the parties were allowed to examine the witness.
None of this is likely to happen in my lifetime. So, perhaps it is simpler to revise the oath to more accurately reflect reality: “Do you swear that the testimony that you are about to give will be the truth and nothing but the truth, and we’ll let the lawyers worry about getting the whole truth out of you?”
Randolph (Tré) Morgan III is an attorney practicing family law and civil litigation in Raleigh, North Carolina. (Editor's note: Attorney Morgan authors a great North Carolina legal blog that can be found at http://northcarolinalegalanswers.blogspot.com. I encourage you to visit.)