For only the third time in history, an American president is facing an impeachment trial, with hearings in the Senate set to start on Tuesday. Such a trial could, in theory, lead to President Donald Trump being removed from office.
He is facing two articles of impeachment, or charges.
Firstly, he is accused of seeking help from the government of Ukraine to help himself get re-elected this November. He is alleged to have temporarily held back millions of dollars of military aid to Ukraine and dangled a proposed White House meeting with Ukraine’s president, both as bargaining chips.
In exchange, witnesses say he wanted Ukraine to publicly announce an investigation into Joe Biden, the man who is leading the Democratic race to challenge him in the election, and whose son was an executive in a Ukraine gas company. Polls suggest Biden would beat him if chosen as the Democratic candidate.
Secondly, after the White House refused to allow staff to testify at the first impeachment hearings last year, Democrats accused Trump of obstructing Congress (the part of the US government that writes and votes on laws, and which was investigating him).
President Trump has denied any wrongdoing and his legal team say the “flimsy” charges are a “dangerous perversion of the Constitution”.
After the four days of opening statements – two days per side – senators will be allowed up to 16 hours for questions to the prosecution and defense, followed by four hours of debate. Only then will there be votes on calling other witnesses.
In the rare event that senators agree to call witnesses, the rules propose that any witness must be deposed and the Senate would then decide which ones, if any, would testify in public.