Rep. Jason CrowJason CrowClark rolls out endorsements in assistant Speaker race Trump-Afghan deal passes key deadline, but peace elusive Cook shifts 20 House districts toward Democrats MORE (D-Colo.), one of the House managers in President Trump's impeachment trial, said Sunday he and other Democrats leading the case against the president in the Senate are considering all "relevant witnesses."

Asked whether House managers are considering calling Lev Parnas, an indicted former associate of Rudy Giuliani Rudy GiulianiGrand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Juan Williams: Breaking down the debates Giuliani criticizes NYC leadership: 'They're killing this city' MORE, Crow told CNN he would not "get into" questions over "any one particular witness."

"All of the relevant witnesses are on the table," Crow added on CNN's "State of the Union."

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Crow added the caveat that "all of this is based on Senate allowing witnesses," which he stressed is necessary in order to have a fair trial, but which Trump's GOP allies have been fighting against.

"[The president deserves a fair trial, the American people deserve a fair trial," Crow said.

“All of the relevant witnesses are on the table,” House impeachment manager Rep. Jason Crow says. “What we have to do is make sure that we have documents too. This can’t be the first [impeachment] trial in American history… where we don’t have documents and witnesses.” #CNNSOTU pic.twitter.com/DNERQMMvpq — State of the Union (@CNNSotu) January 19, 2020

Parnas is a controversial potential witness. He provided additional documents, which were released by the House last week, that appear to corroborate some details central to Trump’s impeachment, including an effort to pressure Ukraine to announce an investigation in former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE, a leading 2020 Democratic presidential contender.

Parnas was indicted for and pleaded not guilty to campaign finance law violations last year. He is reportedly looking for ways to work with the prosecutors in his case who are seeking more details on Giuliani’s dealings in Ukraine.

CNN host Brianna Keilar asked Crow if House managers are considering calling for documents provided by Parnas to be considered in the trial, even if Parnas is not called to testify as a witness.

Crow said that "documents are a great way to assess credibility," but did not say whether that is an option Democrats are pursuing.

The Senate will vote next week on rules for the trial and will likely delay a vote on calling witnesses until later in the process.