(Reuters) - The U.S. Senate impeachment trial of Donald Trump enters a new phase on Friday as senators deliberate and aim to vote on whether witnesses and new evidence should be sought before voting on acquittal or conviction of the Republican president.
Late on Thursday, senators completed two days of questioning of Trump's defense lawyers and House of Representatives Democratic "managers" prosecuting the case against the Republican president.
Here is what to look out for next:
FRIDAY AND BEYOND
* Friday's trial session begins at 1 p.m. (1800 GMT) with impeachment managers and Trump's lawyers spending up to four hours, equally divided, discussing whether witnesses and new documents are needed or not.
Late on Thursday, Republican Senator Lamar Alexander announced he would oppose hearing from more witnesses, dealing a blow to Democrats, even as his fellow Republican, Senator Susan Collins, said she would vote yes.
* A Senate vote is likely on Friday. In the event of a 50-50 tie, the motion fails, unless Roberts casts a vote to break the deadlock. If the Senate votes to hear more evidence, it would then hold subsequent votes on which witnesses senators would like to call and what documents they want to read.
* If the Senate subpoenas witnesses, they would be deposed privately before the Senate decides on public testimony. On Thursday, Representative Adam Schiff, the head Democratic impeachment manager, proposed a one-week limit for conducting depositions.
* If no witnesses or additional documents are allowed to be subpoenaed, senators could consider other motions or proceed to vote on each of the two articles of impeachment, which charge Trump with abuse of power and obstruction of Congress. It is unclear what any additional motions would attempt to do and it could take time for the Senate to work its way through them - possibly extending into Saturday.
* If the Senate decides not issue subpoenas, the trial likely would conclude within days, if not sooner. If it does issue subpoenas, Trump is scheduled to deliver his State of the Union address to Congress on Tuesday with an impeachment verdict likely still undecided.