The evidence against President Donald Trump continues to grow, and now a non-partisan watchdog has accused him of a crime. In the meantime, the impeachment trial in the Senate is almost underway, but we still don't know whether or not Republicans will allow any witnesses to be called.

One of the more shadowy figures involved in the impeachment affair, Lev Parnas, went on MSNBC to share his story last week and contributed his own evidence to the tide now building up against the President. Parnas alleged that he was involved in the surveillance of a U.S. ambassador, that he was a part of the pressure campaign against the Ukrainian government, and that Trump knew about and approved of all of his actions.

Parnas is far from a perfect witness. A former associate of Rudy Giuliani, personal attorney to the President, Lev Parnas was indicted in October for campaign violations and is under considerable legal pressure.

Trump has repeatedly claimed not to know Parnas, and in response, Parnas has released several photos of himself with Trump, as well as three of Trump's children and son-in-law Jared Kushner.

One of the most common reasons Trump supporters give for why he shouldn't be impeached is that he didn't commit any laws, but a new legal opinion released by the Government Accountability Office, a nonpartisan government watchdog, has officially blown that defense out of the water.

"Faithful execution of the law does not permit the President to substitute his own policy priorities for those that Congress has enacted into law," the opinion said. According to the GAO, the Office of Management and Budget, Trump's budget office, "withheld funds for a policy reason ... not a programmatic delay. Therefore, we conclude that the OMB violated" the Impoundment Control Act.

According to the GAO, the Trump Administration broke the law when they withheld defense aid to Ukraine because that aid had been allocated by Congress to be used by the Department of Defense for security assistance. The administration didn't have the right to withhold it.This falls under the Impoundment Control Act which explicitly empowers the Comptroller General of the GAO to report on and bring civil actions against any officials for any breaches.

In response to the GAO opinion, Republican lawmakers and pundits have been trying to downplay the findings or even directly refute them. Alan Dershowitz, one of Trump's most vocal supporters spoke out against the findings on Fox News, and Trump tweeted a quote soon after.

"The GOA got it exactly backwards. Here's what they said. The law does not permit the President to substitute his own policy priorities to those Congress has enacted into law. It's exactly the opposite. The Constitution does not allow Congress to substitute its own priorities..../.... for the foreign policies of the President" tweeted the President.

Meanwhile, the Senate trial is getting under way. The articles were delivered; Chief Justice Roberts was sworn in, and he swore in the Senators. One task still on the to-do list is deciding whether or not to call witnesses. Opinions on the matter are basically split down the party line. Several of the Democratic managers, the Congressmen who will present the case against the President, stopped by the Sunday news shows to urge the Senate to allow witnesses and evidence during the trial.

"The threshold issue here is, will there be a fair trial? Will the senators allow the House to call witnesses to introduce documents? That is the foundational issue on which everything else rests. And one thing that the public is overwhelmingly in support of, and that is a fair trial." Rep. Adam Schiff of California said on ABC's "This Week".

Republicans, on the other hand, are almost universally against calling witnesses. Republicans in the Senate plan to postpone the question of whether or not to call witnesses until after the House managers and the White House have made their arguments and the Senators have asked a round of questions. If they decide not to call any witnesses, this will be the first impeachment in U.S. history to not include witness testimony.

Republican lawmakers took to the news as well to complain about Democrats' treatment of Trump. Sen. David Perdue of Georgia said on NBC's "Meet The Press", "Remember, this week is going to be the first time America gets to hear President Trump's defense. He hasn't had an opportunity to do that yet" despite the fact that the House invited Trump to participate and he declined.