The '580' patent was the subject of an infringement lawsuit filed by eSpeed against Icap subsidiary Garbon.

The jury did find that Garban's trading system infringed on the dealing system covered by the patent licensed to eSpeed, but also found that eSpeed's original patent application didn't adequately describe how the bond-trading system worked.

During the trial, Icap's defence lawyers accused Cantor of misleading the US Patent Office by redrawing its original patent application for a basic bond trading system to add new rules that were already commonly used in the market.

In a statement, Michael Spencer, Group CEO of Icap, says: "We are delighted with the outcome of this case. The jury has found that eSpeed's patent is invalid and we look forward to the judge's decision on whether the patent was acquired by inequitable conduct.

"This is a great result for everyone trading US Treasury products."

An infringement suit brought by eSpeed against BrokerTec - another Icap subsidiary and prime competitor - was over-ruled in a pre-trial motion.

Scandinavian trading technology vendor OMX was also named in the suit against BrokerTec. Last year eSpeed filed for damages against OM Technology for infringement of its patent, but in a statement issued today, OMX says the case against it would not be tried and it faces no liability claims.

In a separate case, a federal judge in Illinois last week backed claims made by Trading Technologies (TT) that eSpeed's dealing system infringes on patents held by the Chicago-based vendor.

TT filed a technology patent infringement lawsuit against eSpeed in August last year. The patents relate to TT's system for displaying multiple prices on a screen so that users can estimate the depth of a market.

In court, Judge James Moran did not issue a preliminary injunction to stop eSpeed using the software but dismissed claims that TT's patent was invalid.