The firm now faces a damages claim for up to £33m plus legal costs.
Former Jones Day lawyer Mohammed Amersi was found to have acted for both the Saabs and the Saudi American Bank on a share placement without disclosing a conflict of interest. Mr Justice Smith was unequivocal in some of his criticism of both Amersi and Jones Day.
It is unlikely the Saabs will pursue the Amersi claim now they have established liability against Jones Day. It is unclear whether the Saudi American Bank will reignite a claim against Jones Day that was stayed pending the outcome of the Saabs' case.
The High Court ruled in favour of the Saabs on key liability issues on 5 December. Jones Day will vigorously resist the damages claim due to be heard next October.