WASHINGTON, D.C. – In order to have a fair trial in the impeachment of President Donald Trump, the Senate must hear from witnesses, Sen. Sherrod Brown said during a conference call Wednesday morning.

Brown, a Democrat from Ohio, accused Senate Majority Leader Mitch McConnell and other Republicans of aiding in a cover-up and running a sham trial.

“It’s just not a real trial unless you have witnesses and evidence,” Brown said during a conference call in which he also talked about safety regulations for buses.

The impeachment trial began Tuesday afternoon and lasted almost 13 hours on the first day. Proceedings continued until almost 2 a.m. Wednesday with deliberations over the rules that will govern the process.

Mostly along party lines, Republican senators rejected 11 proposed amendments from Democrats that sought witness testimony and evidence to be included in the trial.

“Who are they afraid of?” Brown said. “Are they just afraid of the president’s wrath?”

Most of the witnesses Democrats want to hear from are Trump employees and were eye witnesses to the actions that led to the president’s impeachment, Brown said. Trump is accused of abusing his power by asking Ukraine to investigate his political rivals and obstructing Congress by refusing to turn over documents or allow officials to testify in the House probe.

“Why is the defense unwilling to let witnesses come in and say what really happened?” Brown said. “I don’t understand why they’ve fought so hard to leave witnesses out.”

Earlier in the week, Brown said it would be fine if Republicans requested that Hunter Biden testify in the impeachment trial in exchange for witnesses requested by Democrats.

Hunter Biden is the son of Joe Biden, a former vice president and current presidential candidate. Trump asked the Ukrainian government to investigate the Bidens and Hunter Biden’s work on the board of Burisma Holdings, a Ukrainian natural gas producer.

During Wednesday’s conference call, Brown said a push for Hunter Biden to testify is a distraction technique.

“We need to know what happened for sure by people that were there,” Brown said.

McConnell, a senator from Kentucky, hasn’t ruled out allowing witness testimony after opening arguments. However, senators haven’t received assurances that witnesses will be allowed, Brown said.

All 15 previous impeachment trials in the U.S. Senate have included witness testimony. Without witnesses, the current impeachment proceedings would not be a fair trial, Brown said.

“In fact, these were people who were in the room who can shed some light on this,” Brown said of potential witnesses in the trial of President Trump.

Along with trying to rush a sham trial, Brown also accused McConnell of trying to prevent Americans from seeing what is happening during the impeachment proceedings.

The senate majority leader has taken cameras out of the Senate Chamber and cut off regular media access, Brown said. And having proceedings last late into the night discourages the public from watching, he said.

“I don’t mind working until 2 in the morning, but people quit watching,” Brown said.