The Independent Electoral and Boundaries Commission (IEBC) has maintained that the Nyamira governorship elections were done above board.
Speaking before a three-judge bench on Monday in Kisumu, IEBC's lawyer Gilbert Nyamweya said Mr John Nyagarama is the rightful winner.
"In any election in the world, there would be errors but they would not be deliberate but administrative, which cannot nullify the elections."
The case was heard by justices Asikhe Makhandia, Stephen Gatembu and Kathurima Minoti.
Mr Walter Nyambati is in a second attempt to overturn Mr Nyagarama’s win a few months after High Court Judge James Makau quashed the petition filed on February 27.
Judge Makau had ruled that Mr Nyambati of Jubilee Party failed to produce evidence of his allegations.
He said that the irregularities found during the scrutiny of results were insufficient to invalidate Governor Nyagarama's victory.
Mr Nyagarama garnered 65,161 votes against Mr Nyambati’s 58,936 votes.
Mr Fred Ngatia, Mr Nyambati's lawyer, argued that the trial judge erred by presuming that all actions by the IEBC are within the law.
Mr Ngatia added that the number of votes declared in some of the 36 polling stations under review were more than the voter turnout.
"The scrutiny was not in jest. It was not a joking matter but an exercise done by judicial officers. There was variance in the votes because there was clear ballot stuffing, IEBC just doesn’t want to admit," Mr Ngatia argued.
"Errors like this contaminate and pollute results because figures cannot be verified. Let us go back to the electorate, it is their will that will reveal the next governor."
But Governor Nyagarama's lawyer Jones Nyachiro told the court that there were no inconsistencies of the results during the election and after recount.
The judgment will be made on July 26.