Five of six brokers on trial at Southwark Crown Court in London have been acquitted of rigging the Libor benchmark rate.
The six were alleged to have conspired with Tom Hayes, who became the first person convicted of rigging Libor rates in August.
The verdict is a blow for the Serious Fraud Office, which brought the charges.
Prosecutors alleged that the six passed on requests from traders on where to set the London Interbank Offered Rate, which is used to calculate the interest that banks charge when lending to one another for hundreds of trillions of dollars-worth of financial contracts and loans.
The six brokers on trial were Darrell Read, Danny Wilkinson and Colin Goodman from Icap, Noel Cryan from Tullett Prebon, and Jim Gilmour and Terry Farr from RP Martin.
The brokers allegedly gave one another nicknames like Big Nose, Lord Libor and Sarge and were rewarded by Hayes, a client, for their assistance.
Five of the six were acquitted and are free to go. The jury is yet to reach a verdict on a second count against Darrell Read, Reuters said.
Tom Hayes, a former trader in yen derivatives at the Swiss bank UBS, was found guilty of conspiracy to defraud in August after a nine-week trial.
