WASHINGTON -- 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" 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.
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," Seidman said.
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 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 investigation 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.