What is the standard of proof senators will apply to the impeachment trial of President Donald Trump? It depends on whom you ask. 

The Constitution provides only bare-bones instructions on the impeachment framework. It does not outline a “standard of proof.”

Some legal experts have argued that the seven Democratic House managers  must prove “beyond a reasonable doubt” that the president abused his office and obstructed justice, as in a criminal trial. Others contend they must merely present a “preponderance of evidence” to support their impeachment articles, as in many civil cases.

[‘Documents don’t lie’ — the other fight over evidence at Trump impeachment trial]

The reality is such concerns over the standard of proof seldom make a difference in any kind of trial, with numerous jury behavior studies showing jurors assess evidence the same way regardless of their instructions.

“My intuition is that this is likely to be even more true with regard to politicians,” said Louis Michael Seidman, the Carmack Waterhouse Professor of Constitutional Law at Georgetown University Law Center. “Either you think that Trump should be impeached or you don’t. In the real world, people just don’t focus on abstract questions like the standard of proof.” 

That doesn’t mean Congress has ignored the subject in the past. 

In the 1986 impeachment trial of federal District Court Judge Harry E. Claiborne, senators debated for hours before voting down, 75-17, a motion by Claiborne’s defense team to designate “beyond a reasonable doubt” as the standard. Claiborne was removed from office.

The question of standard of proof has been revived at subsequent impeachment trials. In 1991, District Court Judge Alcee L. Hastings, now a Democratic House member from Florida, was impeached and removed for his involvement in a bribery scheme. The case united some of the most liberal and conservative senators in Hastings’ defense, with former Utah GOP Sen. Orrin G. Hatch, an advocate for the “beyond a reasonable doubt” standard in the Claiborne trial, joining forces with the likes of then-Sen. Joe Biden of Delaware over doubts about the circumstantial nature of the evidence.

Trump has sought to cast doubt on testimony from “2nd and 3rd hand witnesses” that House Democrats heard during their probe into his alleged abuse of power scheme involving Ukraine and that underpins the impeachment articles. His House GOP allies echoed his protests about insufficient evidence as one of their central arguments against the impeachment process.

The White House blocked firsthand witnesses such as acting Chief of Staff Mick Mulvaney and former national security adviser John Bolton from testifying.

Diverging schools of thought

Over the decades, impeachment defendants and their counsels have argued for the stricter “beyond a reasonable doubt” standard because of parallels between some impeachment language in the Constitution and the language governing criminal courts, including use of the words “try” and “convicted.”

But the punishment for the individual convicted in an impeachment trial is far less severe than punishment in criminal cases, proponents of a less burdensome standard have countered. A criminal court can strip a defendant of his life, liberty and property. An impeachment conviction only involves removal from office and prohibition from holding public office.

In the case of presidential impeachments, senators must also consider that a conviction, in essence, overturns the will of the Electoral College. This is acknowledged from everyone to the Founding Fathers to Trump impeachment proponents like House Judiciary Chairman and impeachment manager Jerrold Nadler.

The gravity of this consequence is a double-edged sword for the debate over how strictly senators should interpret the standard of proof in an impeachment trial, constitutional law scholar Charles Black wrote in his “Impeachment: A Handbook,” first published in 1974 and updated since.

“The adoption of a lenient standard of proof could mean that this … frustration of popular will could occur even though substantial doubt of guilt remained. On the other hand, the high ‘criminal’ standard of proof could mean, in practice, that a man could remain president whom every member of the Senate believed guilty of corruption, just because guilt was not shown ‘beyond a reasonable doubt.’ Neither result is good; law is often like that,” Black writes.

Black recommended senators seek an “overwhelming preponderance of the evidence” to convict a president, a standard that falls somewhere between the onerous “beyond a reasonable doubt” and a mere “preponderance.”

But Black ultimately demurred, saying that each senator “must find his own standard in his own conscience, as advised by reflection.”