Awiti's election was nullified on February 2018 by the High Court.
Court of Appeal judges Philip Waki, Fatuma Sichale and Otieno Odek upheld the nullification on July 19.
Authorities said security has been bolstered to avert potential ugly scenes by opposing camps.
Homa Bay County Governor Cyprian Awiti will on Thursday afternoon know whether he will finish his second term in peace or if his political nemesis Oyugi Magwanga will get another chance to wrestle the seat from him.
Mr Awiti lost both at the High Court and Court of Appeal but moved to the apex court arguing that it was wrong for the judge who nullified his election to ignore scrutiny and recount of votes, which still put him ahead of Magwanga.
Arguing before the Supreme Court, Mr Awiti through Prof Tom Ojienda said the judges — despite acknowledging that Justice Joseph Karanja erred in law by completely failing to consider the scrutiny — still dismissed the appeal and ordered the Independent Electoral and Boundaries Commission (IEBC) to conduct a fresh governor’s election.
Mr Ojienda said the scrutiny as ordered by the trial judge was part of the evidence and it was, therefore, wrong for the two courts to ignore the report. He told Chief Justice David Maraga, Justices Mohamed Ibrahim, JB Ojwang, Smokin Wanjala, Njoki Ndung'u and Isaac Lenaola that had the two courts considered the report, the outcome would not have been nullified.
He said all the allegations made by Mr Magwanga in his petition were discounted in the scrutiny yet the court chose to believe the evidence of one witness, who testified that there were alterations.
Mr Ojienda said a summary presented in court clearly discounted the narrative that there was deliberate alteration of between 100-200 votes, which were allegedly taken from Mr Magwanga and transferred to Mr Awiti.
“There was not a single polling station that was scrutinised that proved the lie fabricated by the respondents. In fact, if at all there was any error in counting, it was an error of either one or two votes. More importantly, all the counterfoils were traceable to the ballot papers,” he said.
IEBC also supported the argument, saying the forms supplied by Mr Magwagwa, which showed alterations, did not originate from the poll agency.
The Commission defended the outcome saying the ballot boxes were safely secured and claims that they were tampered with after the polls, were false.
On his part, Mr Magwanga through lawyer Charles Kanjama said the scrutiny could not be relied upon because there were efforts to suppress the will of the voters.
According to Mr Kanjama, there was a systematic reduction of Mr Magwagwa's votes and the forms they provided to the court showed the alterations.