"It's as if uncovering corruption has become a crime," Geneina, who headed Egypt's Central Auditing Authority, says in his villa in a plush Cairo suburb.
President Abdel Fattah al-Sisi, who had promised to tackle corruption, abruptly sacked the 62-year-old retired judge in March.
Since then, an intense campaign by Egyptian media, which rarely dares to criticise Sisi's governance, has now seen Geneina and his family accused of tarnishing the country and having links with the banned Islamist opposition.
Quoting a study by the authority using reports between 2012 and 2015, Geneina calculated the cost of corruption at about 600 billion Egyptian pounds ($66 billion, 60 billion euros).
The study highlighted the allegedly illegal acquisition of state-owned land by senior officials and businessmen from the tenure of toppled president Hosni Mubarak.
Geneina is convinced that his sacking and trial is based on an erroneous media report which suggested he attributed the 600-billion figure to 2015 alone.
He is accused of "spreading false news with the goal of harming public interest," and the prosecution claims Geneina used "baseless calculations" to exaggerate the cost of corruption.
"Where were you all these years if I was dangerous to the state?" he asks. "Why wasn't I unmasked earlier by security and intelligence agencies?"
Watchdog Transparency International ranks Egypt as 88th on its corruption perceptions index, and Sisi has publicly launched a crackdown on the widespread graft that dogged the Mubarak years.
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In September, he sacked his agriculture minister who was later sentenced to 10 years in prison for taking bribes.
Geneina, who rose through judicial ranks in his 34-year legal career, believes Egypt's fight against widespread corruption has been piecemeal.
"We can't set an example with words alone. We need action," he says. "Could (my trial) be because the studies implicated bodies that were never named until now?"
The charges against Geneina came during a crackdown on opposition groups overseen by Sisi since the then-army chief toppled Egypt's first democratically elected president Mohamed Morsi in July 2013.
The former magistrate, whom Morsi had appointed to head the anti-corruption authority, criticised the "stranglehold" that security agencies still have over Egyptian state institutions.
Geneina's fall from grace now also risks bringing his eldest daughter down with him.
Shorouk, 27, a former employee of the international law firm Baker and McKenzie, was last month sacked from the administrative prosecution after sharing a cartoon on Facebook of a former justice minister.
"This is part of a score settling," Geneina says, his daughter by his side.
Amr Adly, an economist at the Carnegie Middle East Centre, says Geneina's calculation of the cost of corruption is flawed, but the authorities' reaction has been "disastrous on a political level".
Even if the figures provided in Geneina's study were inaccurate, prosecuting him "gives the impression that the executive takes revenge on those who talk about corruption," Adly says.