Is former President Donald Trump's impeachment trial by the Senate constitutional? According to George Washington University law professor and Fox News contributor Jonathan Turley, the matter is a "close question."

Turley joined Sandra Smith and John Roberts on "America Reports" Tuesday to offer his insight on the second impeachment of the 45th president. 

JONATHAN TURLEY: IMPEACHING TRUMP – HOUSE THREATENS TO TRASH THIS CORE PRINCIPLE TO ENSURE CONVICTION

JONATHAN TURLEY: All of us agree this is a close question. Most people have a default one way or the other. I tend to default more with the text. And I think the better argument is probably the narrower argument, that you don’t really have room for retroactive trials under the text.

I think in the end, you have a very interesting and unresolved issue. I have evolved in my view of the text, and I actually still agree ... there’s value in the retroactive trials, [it's] just you have to balance them against these costs and against the text.

First of all, I thought it was a very good performance by these managers. I thought [Rep. Joe] Neguse [D-Colo.] was very, very good.

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They began with this highly emotive narrative with this video, which was remarkably detached from the issue facing the Senate. Everyone agrees that what happened on January 6th was horrible, was despicable. It was a desecration as much as an insurrection. But that doesn’t go to this question of whether we should open this door to retroactive trials.

[On previous impeachment trials of officials who had already left office] There are only two cases, and the outcomes do not support this. In [the case of Sen. William] Blount, they dismissed the case for jurisdictional reasons [in 1799]. And in [the case of former Secretary of War William] Belknap [in 1876=, almost half of the Senate dismissed because they believed that it was unconstitutional, and then they went on to acquit him.