Facts

Parties and context. The respondent plaintiff, a Spanish national domiciled in Spain and a wealthy businessman, held an undeclared account with bank [C.] and was the beneficial owner of two offshore Panamanian companies ([D.] Corp. and [E.] Inc.), whose assets were deposited in the United States.

Opening of the disputed account. In 2000, the plaintiff entrusted part of his assets to the appellant bank and/or to [H.] , an asset manager employed by the bank since 1999 and the son of one of the plaintiff's close friends. The disputed account was opened by [H.] in the name of his own father, and not in the plaintiff's name, by falsely leading the plaintiff to believe that it had been opened in his name. The plaintiff ordered the transfer of his assets (CHF 1'377'529.15, USD 204'945.96 and EUR 159'477.10) to this account.

Offshore transfers. In 2003 and 2004, the offshore companies caused amounts (USD 1'726'857.36, then USD 962'394.05 via another account) to be transferred to the disputed account. It is not disputed that these companies had no relationship with the bank and that, for traceability reasons, they intended only to pay funds destined for the disputed account. The plaintiff alleges that these transfers were made on his instructions, which the bank disputes.

Misappropriation. [H.] , dismissed in 2011 with effect from 30 June 2011 but retained as an external independent manager, misappropriated the entirety of the assets of the disputed account through some thirty withdrawals between 2003 and 2012, and then closed the account. He gave the plaintiff false statements of wealth. The plaintiff learned the truth only on 15 November 2012. [H.] was charged with forgery of documents, breach of trust and, in the alternative, fraud.

Cantonal proceedings. The plaintiff brought an action for liability against the bank based on art. 55 CO, by a claim filed on 23 June 2017 before the Court of First Instance of Geneva. His principal claims nos. 2 to 4 concern the amounts he himself transferred; his principal claims nos. 5 to 10 concern the amounts transferred by the offshore companies; his alternative claims concern the 33 withdrawals. The proceedings were limited to standing to sue. By judgment of 23 November 2018, the court admitted standing to sue for claims nos. 2 to 4 and denied it for claims nos. 5 to 10. Ruling on the plaintiff's appeal on 18 June 2019, the Civil Chamber of the Geneva Court of Justice recognised standing to sue for claims nos. 5 to 10 and for all of the alternative claims.

Appeal. The bank lodged an appeal in civil matters on 2 September 2019, contesting only standing to sue on claims nos. 5 to 10 and the alternative claims, and alleging a violation of art. 55 CO (the condition of damage and the erroneous identification of the assets of the offshore companies and of their beneficial owner). The plaintiff seeks a finding that the appeal is inadmissible, considering that the conditions of art. 93 para. 1 let. b FSCA are not met.

Considerations

Admissibility in general and the concept of a final decision. An appeal in civil matters against interlocutory decisions is admissible only if they may cause irreparable harm (art. 93 para. 1 let. a FSCA) or if the admission of the appeal may immediately lead to a final decision avoiding lengthy and costly evidentiary proceedings (art. 93 para. 1 let. b FSCA). The appellant relies only on this second hypothesis. The Federal Supreme Court definitively resolves a controversy by holding that a partial decision, a partially final decision within the meaning of art. 91 FSCA, is covered by the concept of a final decision in art. 93 para. 1 let. b FSCA, regardless of whether it ends the whole of the first-instance proceedings.

Cumulative conditions of art. 93 para. 1 let. b FSCA. Two cumulative conditions must be met: first, the Federal Supreme Court must be able, by admitting the appeal, to immediately render a final or partially final decision by reforming the contested judgment; second, this decision must make it possible to avoid lengthy and costly evidentiary proceedings. The Federal Supreme Court cannot render such a decision where, if the appeal were admitted, it would have to annul the contested judgment and remit the case to the cantonal authority for supplementary investigation and a new decision.

Employer liability (art. 55 CO) and standing to sue. Standing to sue forms part of the substantive conditions of the claim and is therefore determined by substantive law. According to art. 55 para. 1 CO, the employer is liable for damage caused by its auxiliaries in the performance of their work, unless it proves that it took the care required by the circumstances. This is a simple strict liability for the acts of others, requiring six conditions, including an unlawful act by the auxiliary, damage, a causal link and a lack of diligence on the part of the employer (the last two conditions being presumed). Only the direct victim, who suffers direct damage to his assets, has standing to sue; a third party who suffers only reflected harm has in principle no right. Standing to sue is closely linked to the unlawfulness of the act; in the case of purely economic damage, the violated rule must protect the victim in the rights affected (objective conception of unlawfulness).

Absence of sufficient findings by the cantonal court. The cantonal court relied on a threefold rationale: first, that the offshore transfers had been made…