A Canadian investment bank was properly held liable for aiding and abetting a breach of fiduciary duty on the part of the board of directors of Rural/Metro Corp. in its acquisition by Warburg Pincus, a global private equity firm, the Delaware Supreme Court ruled unanimously Monday.

Justice Karen L. Valihura, writing for the high court en banc, affirmed a decision of the Delaware Court of Chancery holding the investment bank, RBC Capital Markets, liable for more than $75 million in damages suffered by shareholders in Rural/Metro, a for-profit provider of medical transportation services.

In a 105-page opinion in the case, captioned RBC Capital Markets v. Jervis, Valihura said Vice Chancellor J. Travis Laster correctly held RBC Capital Markets was liable for 83 percent of damages claimed by Rural/Metro stockholders who said their shares were undervalued because directors made decisions that fell outside the range of reasonableness during the process leading up to the merger, and when approving the merger; and because directors failed to disclose material facts in the proxy statement that set up a shareholder vote on the merger.