By Frank Bowman

Over the past few weeks, the requirement of Article I, Section 3, of the Constitution that senators, when sitting in trials of impeachment, “shall be on oath or affirmation,” has provoked some heated discussion. The Constitution does not prescribe a particular form of words, but, by tradition, senators now declare that, “I, [name], solemnly swear, (or affirm, as the case may be,) that in all things appertaining to the trial of the impeachment now pending, I will do impartial justice, according to the Constitution and laws: So help me God.”

Democrats have decried Senate Majority Leader Mitch McConnell’s statement that he is not impartial and will coordinate trial strategy with the White House as a preemptive violation of this oath. Others have suggested that the oath implies an obligation by all senators to pursue relevant evidence by adopting rules that authorize Senate subpoenas to recalcitrant administration witnesses.

These may be effective rhetorical ploys, but as a constitutional matter, the oath requirement probably doesn’t compel any particular action.

In truth, we don’t really know what the Framers had in mind with the senatorial oath requirement. Some commentators have suggested that it was meant to emphasize that the Senate proceeding, in which the Senate has “the sole power to try all Impeachments,” is to be a trial-like process with trial-like rules. But that’s pure speculation, and it doesn’t really help very much even if true. To say that an impeachment trial should have some attributes of trials in other settings just doesn’t get us very far.  The Supreme Court, in its only case on the minimum requirements for a Senate impeachment trial, U.S. v. Walter Nixon, said that the word “trial” doesn’t imply any particular procedural rules.  In essence, it found that the Senate can adopt pretty much any rules it likes short of deciding cases by coin flip.

Moreover, trying to analogize Senate trials to, for example, ordinary jury trials and senators to jurors (or even judges) just doesn’t work. The distinctive function of criminal and civil trial juries is that the judge tells them the law — i.e., what facts the plaintiff or prosecution must prove — and then the jury is to perform the very narrow task of deciding if the facts have been proven to the requisite degree of certainty (beyond a reasonable doubt in criminal cases, or to a preponderance of the evidence in civil trials).  Juries are never asked if the facts they have found should matter. 

For example, if the CEO of a corporation is tried for fraud, the jury is asked to decide whether Elements A, B, C, and D of the crime the law calls “fraud” have been proven, but they are not asked if fraud should be a crime in the first place.  Nor are they asked to consider whether this particular fraud by this defendant under these circumstances ought to be excused because it’s just not serious enough. Nor are they allowed to decide to wave away the whole affair because, on balance, the defendant has been a good CEO and removing him would be bad for the corporation.

Yet this is exactly what the senators are charged with doing in an impeachment case.  They find facts, yes, but they are also the judges of the law, by which I mean the questions of whether the proven facts amount to an impeachable “high crime or misdemeanor” and whether the president’s conduct ought to result in removal from office.

What’s more, unlike jurors in a court case, or even judges in such cases, senators as a body are not bound by any preexisting rules of procedure or evidence.  They are entitled to make such rules as seem appropriate to them at the outset, and to change them by majority vote in the middle of the trial if they like. 

In the end, I think the oath requirement has, and perhaps was intended to have, three related functions. First, it emphasizes the solemnity of the occasion.  Second, it admonishes senators to be honest in their judgments of the facts and, so far as possible, not swayed by partisan allegiances or personal political considerations.  Third, it reemphasizes the oath senators take upon assuming office to support and defend the constitution insofar as the impeachment trial oath charges senators with making judgments consistent with maintenance of constitutional order and promotion of the national interest. 

Therefore, one can fairly argue that the oath requirement calls senators to examine their motives and their consciences both when framing the original trial rules and in subsequent votes on process and substance.  Such an examination should tilt in favor of insistence on full production of evidence by the administration.  It should also, at least in my view, dispose senators to uphold the law, long-accepted norms of presidential behavior, and the institutional prerogatives of their own chamber even at some political risk.

Sadly, however, other than as a basis for an appeal to conscience, and when that fails, as a rhetorical club with which to thrash Republican senators, I don’t think the oath requirement has much practical value.