She argued that it was pointless to spend billions of taxpayers' money only for such a critical task to be left in the hands of one person.
"Why do we need a commission of seven people?" the lawyer said and asked the Supreme Court to declare Regulation 87 of the IEBC general regulations unconstitutional.
The said regulation grants the IEBC chairperson the power to tally and verify results, a reason cited by Chebukati in response to the petitions questioning his alleged unilateral actions.
Ms Janmohamed argued that the Supreme Court had settled the matter in 2017, establishing guidelines that the IEBC was to employ during the August 9 General Election.
"The Supreme Court told you that you cannot do this (act unilaterally) and you did nothing," she said.
As a consequence, she wants Ruto's win nullified and Chebukati barred from conducting any other election or holding public office for breaching Chapter Six of the Constitution on Leadership and Integrity.
She also faulted the IEBC boss for calling off Mombasa and Kakamega governor elections, as well as other constituency and ward contests just a day before the elections, claiming that it was a voter-suppression tactic.
Ms Janmohamed cited voter turnout of Mombasa and Kakamega, "at 44 and 57 per, cent respectively", as significantly lower than the national turnout of 65.4 per cent as initially announced by the commission. IEBC Chairman Wafula Chebukati. [Boniface Okendo, Standard]
"What happens when someone decides to cancel the presidential election on the basis of an emergency?" posed the lawyer, faulting Chebukati's response that there had been a mix-up of ballot papers.
Ms Janmohamed also said it was offensive that Mr Njoroge's petition had been referred to as a "surrogate petition" and a "proxy petition" by Ruto, in his response.
"John Njoroge Kamau went to the polling station to vote for his preferred president," she said, adding that as a result of the public spat between IEBC commissioners, her client did not believe the presidential election was transparent, credible, verifiable, or even secure.
"Was this election verifiable and accurate? Chebukati said it was. Four commissioners are saying it was opaque. All parties say that they won. Where does the voter go?
"We shouldn't be in a position where we hope our votes will count. We should be in a position where we know our votes will count," she said.
Four commissioners - vice-chairperson Juliana Cherera, Irene Massit, Francis Wanderi, and Justus Nyang'aya - have accused Chebukati of coming up with "his own results."
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Ms Janmohamed raised issues similar to those of Azimio la Umoja-One Kenya leaders Raila Odinga and Martha Karua, the first and second petitioners, who also want Chebukati barred from conducting any election, citing criminality.
Mr Odinga's and Ms Karua's lawyers also argued that it was unlawful for Chebukati to tally and verify results on his own. They further accuse him of suppressing voter turnout in their strongholds of Mombasa and Kakamega by suspending governor elections.