Parliament Speaker Amason Kingi said they expect the Deputy President to testify.
“Unfortunately, this is a time-limited process,” he said, adding that the impeachment trial cannot legally be extended beyond Friday.
The speaker said the case could then proceed without him, or “for exceptional reasons” he could appear later, citing the rules of court procedure.
Speaking to local Citizen TV, Senator Daniel Maanzo said it was an exceptional trial and that another “new exceptional situation that is not even provided for by law” had arisen, saying they would make statements to push the speaker for a ruling.
He said the vice president “just looked tired” but was having lunch in his office with other senators who said he was fine and all expected him to appear for the defense.
His removal from office requires two-thirds of the 67 senators.
He faces 11 charges, including corruption, inciting ethnic divisions and subverting the government.
When the trial began on Wednesday, the vice president pleaded not guilty to each of the charges as they were read to the house.
An overwhelming majority of members of the National Assembly last week voted to approve his impeachment, setting the stage for a trial in the Senate.
He fell out with President William Ruto just two years after they were elected on a joint ticket.
The dispute came to a head in June when Gachagua, acting as a presidential undercut, accused the head of the intelligence agency of failing to properly inform Ruto and the government of the scale of mass protests against an unpopular tax hike.
In a major blow to his credibility, Mr Ruto has just been forced to withdraw taxes. He dismissed his cabinet and introduced opposition representatives into the government.
Mwengi Mutuse, the petitioning lawmaker, appeared in the Senate as a witness on Wednesday, accusing Gachagua of violating the constitution in taking away the house through the various grounds of his petition.
He framed the allegations against the vice president as “extraordinary” wrongdoing that merited impeachment. He gave the example of Gachagua’s remarks that the government is like a stock company, suggesting that only those who voted for the government will benefit in terms of development and services.
He also accused the vice president of acquiring vast wealth through corruption, among other allegations.
The lawmaker was then criminalized during cross-examination and at times appeared to struggle to defend his testimony.
A clip of President Ruto addressing the rally was played in the Senate, where he described the people of Murang’a, in central Kenya, as the government’s “major shareholders”.
Gachagua’s lawyers asked Mutusa how the vice president could be accused of “helping” the president.
The deputy was also required to substantiate the basis of the assessment of the wealth allegedly acquired by the vice president.
Gachagua is accused of acquiring assets worth 5.2 billion Kenyan shillings ($40m; £31m) in the two years since he became vice president – allegedly acquired through corruption.
He said most of the property in question was from his late brother’s estate.
During the trial, one of Gachagua’s lawyers, Elisha Ongoya, said that all the allegations against the vice president were “either false, ridiculous or embarrassing.”
Andrew Mulwa, the former chief executive of the Kenya Medical Supply Agency, who was the second witness, faced tough questions over his claims that he was intimidated by a call from the deputy president asking him to return documents for the canceled tender for mosquito nets, which the president accused of meddling .
“This was the first time that the acting deputy president called me and requested documents that are under investigation. Mr. Speaker, in my 15 years of public service, I have never been asked for this,” he said.
Gachagua dismissed the allegations as “ridiculous and baseless” and his legal team noted that it happened when the process had already been completed and argued that no money had been lost
A third witness, the Ethics and Anti-Corruption Commission’s deputy chief executive, Abdi Mohamud, testified about allegations of a conflict of interest related to the matter, as well as allegations that the vice president received gifts of cows from the public.
It was planned that the trial would last until the end of the day, and the deputy president would speak himself.
At the end of the process, senators will discuss the proposal and then vote.
The deputy president is a wealthy businessman from the vote-rich central region of Mount Kenya.
In just five years, he went from being the first member of parliament to second in command in Kenya after Ruta chose him as his running mate in the August 2022 elections.
His impeachment trial has dominated discussion among many Kenyans and the media in recent weeks.
Many observers expect impeachment to happen if the opposition supports the ruling coalition, as it did in the National Assembly.
Gachagua is expected to challenge the decision if it is handed down.
Kenyan media are already reporting on his possible replacements, with four people mentioned:
