The United States Secret Service has confirmed that the Sh2 billion found stashed in a client's safe deposit box at a Barclays Bank branch was fake.
In a document filed in court, investigative specialist Gilbert Gunn disclosed that the notes lacked requisite security features.
"My examination of the 13,194 specimen notes determined they are counterfeit because they do not contain the authentic security features found in genuine US Federal Reserve notes," said Mr Gunn.
Mr Gunn explained that genuine US currency contains red and blue fibres, intaglio printing, typographic printing, a security thread, watermark, colour shifting ink, micro printing, a 3D security ribbon and a colour shifting bell.
These features apply to notes printed in 1996 and 2004, he noted.
Mr Gunn's revelations are contained in a letter through which he responded to a request by a Mr Richard Cherwiyot from the DCI, for verification of the authenticity of the currency.
The document has been tabled in court as part of evidence presented by the Directorate of Criminal Investigations, the Director of Public Prosecution and Barclays Bank.
Mr Gunn gave the details amid investigations into a case that resulted from a suit by Erick Otieno Adede, a lawyer and international consultant, against the DCI, DPP and Barclays Bank.
Mr Adede was arrested on March 19, alongside traders Mohamed Ejaz alias Shah, Mary Wanjiru Mwangi alias Elizabeth Muthoni and Irene Wairimu Kimani after detectives found the fake money.
While insisting that the currency was genuine, he asked the DCI to present it in court.
Mr Adede and the others faced a joint charge of conspiring to defraud businessman Muriithi Materi Mbuthia of Sh20 million at the bank's Queensway branch, while pretending to be investors.
He pleaded not guilty to allegations that police found $20,067,900 (Sh2 billion) in fake money and 41.373 kilogrammes of brass at the bank.
The lawyer was released on a cash bail of Sh1 million while the rest paid Sh300,000 each.
The DCI and the DPP have termed Mr Adede's suit "fatally incompetent".