Trump says he has been denied due process. But the Constitution does not afford him that.

Kristine Phillips | USA TODAY

Show Caption Hide Caption Presidential impeachment: Clinton, Johnson, Nixon test U.S. democracy Presidents have been impeached, but none have been removed from office due to impeachment. Confusing? Here's how.

WASHINGTON – In a six-page invective to House Speaker Nancy Pelosi, President Donald Trump contended he has been more wronged in the impeachment proceedings than even the 17th-century women who were hanged based on dreams, visions and confessions elicited by torture.

"More due process was afforded to those accused in the Salem Witch Trials," the president wrote.

His allies have made similar arguments, though not quite so hyperbolic. They said the president has been railroaded based on hearsay evidence. They argued he has been deprived of the right to face his accusers. They claimed the House's impeachment proceedings would not have been allowed in a court of law.

But legal experts say this criticism, peppered with terms borrowed from criminal proceedings, is based on a misinterpretation of what the Constitution says about impeachment and how much protection it gives the president.

The answer: Not much.

Like Bill Clinton in the 1990s and Andrew Johnson more than a century earlier, Trump does not have the same constitutional protection afforded to a criminal defendant, they said.

"The president of the United States takes the presidency conditioned on the fact that he may be subject to impeachment," said Michael Gerhardt, a University of North Carolina law professor. "He has no entitlement to demand due process."

To compare the president – any president – to a common criminal defendant is misleading, experts say. Here's why.

Crime, punishment and due process

For one, Trump is not a defendant accused of a crime defined by statute, like theft or murder.

"What is and is not considered an impeachable offense is not predetermined by law," said Frank Bowman, a University of Missouri law professor. Although the Constitution describes an impeachable offense as "treason, bribery, or other high crimes and misdemeanors," that standard is broad by design.

This means jurors – senators with their own political alliances – decide what the facts are and whether they matter, Bowman said.

No other jury in the U.S. has that much power. Jurors in criminal trials are simply asked to weigh the evidence and decide whether it proves a crime.

Impeachment: Trump's trial in Senate likely to be more partisan than Bill Clinton's was in 1999

Perhaps one of the most basic differences between an impeachment trial and a criminal trial is the punishment if someone is convicted. Presidents lose their office, which has never happened and is highly unlikely to happen to Trump. Criminal defendants can lose their freedom, and that happens regularly.

This brings us to due process. The Fifth Amendment says no one can be deprived of "life, liberty or property" without due process of law. A president facing an impeachment trial is not at risk of losing life, liberty or property.

Congress "is not obliged to follow due process, (though) it may well decide to provide things that look like due process," Gerhardt said.

Due process, at a minimum, requires an impartial decision-maker. "You can see how that doesn't really apply to impeachment," he said.

No impartiality

Senators in an impeachment trial are required to take an oath promising to be impartial.

But Senate Majority Leader Mitch McConnell, R-Ky., has said he is "not impartial about this at all." He has guaranteed Trump's acquittal, telling Fox News host Sean Hannity there's "zero chance" the president will be removed from office.

McConnell blasts House over Trump impeachment Senator Mitch McConnell, the top Senate Republican, denounces the "unfair" House impeachment of President Donald Trump and reassured Trump and his supporters that "moments like this are why the United States Senate exists.” (Dec. 19)

"In the past," Bowman said, "senators try to maintain at least the fiction of impartiality, to maintain at least the notion that they could be persuaded. What we have with McConnell ... is essentially a statement that there's nothing you can do that's going to persuade us: We're the president's men and women, and he's going to stay in office."

Democrats may see this as brazen, but it's not unconstitutional.

In a criminal trial, lawyers probably would keep someone off the jury if he declared as little impartiality as McConnell.

In an impeachment trial, senators can't be disqualified if they express bias. That makes sense, Bowman said. Otherwise, "the majority will just disqualify the minority and you have this sort of bizarre free-for-all, with six people left standing. It will be silly."

Presentation of evidence, testimony

The Senate decides how evidence will be presented or whether it will be presented at all. Though the chief justice of the Supreme Court presides over the trial, for the most part, he has no control over the rules.

"The Senate can pretty much make any rules it pleases that aren't just barking mad," Bowman said.

The only two instances in which the Senate has held an impeachment trial of a president show how widely the rules can differ.

Johnson was impeached for violating a law forbidding a president from removing certain government officials without Senate approval. His 1868 impeachment trial was a spectacle that lasted almost two months. House managers – the equivalent of prosecutors – introduced documents and testimony supporting 11 articles of impeachment.

More: Pathway of the impeachment process: How it works, where we are

Forty-one witnesses, including 16 from Johnson's defense team, testified before a packed Senate gallery.

Like a criminal trial, an impeachment trial has opening and closing arguments. With Johnson, closing arguments by the House managers and the president's attorneys lasted 11 days.

Clinton's impeachment was spurred by an investigation into financial dealings before he became president, which shifted to a scandal about an extramarital affair. His trial in 1999 was far more subdued, abbreviated and secretive.

Senators heard opening and closing arguments, submitted written questions that were read aloud by the chief justice, and voted on whether to call witnesses. Only three witnesses, including Monica Lewinsky, testified. But they did so behind closed doors, and videotaped portions were shown to the full Senate.

In Trump's case, lawmakers are deadlocked on how to proceed after the House approved two articles of impeachment.

Pelosi signaled she may delay sending the articles to the Senate until it sets procedures she thinks are fair. But the two Senate leaders are at an impasse.

Senate Minority Leader Chuck Schumer, D-N.Y., has proposed that four witnesses testify, including former national security adviser John Bolton and acting Chief of Staff Mick Mulvaney. Neither testified during the House impeachment proceedings.

Schumer said the Senate needs to see documents, including White House records related to withholding military aid from Ukraine. Trump is accused of withholding that aid and a White House visit in order to pressure Ukraine's president to announce investigations that would help Trump politically.

Chuck Schumer: Mitch McConnell provides no defense for Donald Trump Democratic leader Chuck Schumer rebutted the top Senate Republican on Thursday after he denounced the House impeachment of President Donald Trump as "most unfair." (Dec. 19)

McConnell said on "Fox and Friends" that Republicans "haven't ruled out witnesses," but he also indicated he's not eager to hear from new ones. He said the Senate should adopt the same rules as for Clinton's trial.

"Fair is fair," McConnell said.

This sort of procedural debate is very unusual in criminal trials, which are guided by well-established procedures and rules of evidence. Rules for impeachment trials, however, are what the Senate decides they should be.

Is there a burden of proof in an impeachment trial?

Not formally.

The Senate has declined to define what burden of proof is required to remove a president, a vice president, legislators, judges and other civil officers.

During the 1986 impeachment trial of U.S. District Judge Harry Claiborne, who filed false tax returns, his attorneys argued the charges against him should be proven to the same standard as in a criminal trial: "beyond a reasonable doubt." They argued that impeachment and criminal proceedings both lead to consequences for the accused.

But in deciding whether a president committed high crimes or misdemeanors, "each senator decides for himself or herself what the burden of proof is," Gerhardt said. "There's a lot of making stuff up here."

More: Donald Trump promotes White House aide who refused to testify in impeachment inquiry

During Clinton's impeachment trial, several senators from both parties said they believed the standard should be as high as in criminal trials. But they disagreed on whether House managers had proven their case to that standard.

For example, former Sen. Jeff Sessions, R-Ala., voted to convict, saying House managers had proven beyond a reasonable doubt that Clinton had committed perjury and obstruction of justice.

Using the same standard, however, other Republicans reached a different conclusion. Former Sen. John Warner of Virginia and Sen. Richard Shelby of Alabama voted to acquit Clinton of perjury but convict him of obstruction.