Facts

Parties and court : The appellant, [A.] , was hired as a senior geologist by the Geneva branch of [B.] Limited (the company, the employer) from 1 September 2006, and was later promoted to technical director (level 26 of the internal scale). He reported to the technical director for Africa. His gross annual salary amounted to CHF 369'500, to which a bonus and LTIP plan benefits were added.

Restructuring context : From 2015, rumours of dismissals circulated. On 16 September 2015, the company announced the elimination of seventy positions in Geneva, then offered a voluntary departure programme on 22 September 2015, to which the appellant was a recipient.

Disputed downloads : After an employee suspected of downloading was reported, the company set up, on 17 and 18 September 2015, a daily alert for any download of more than 1 GB per day and per user. On 30 September 2015, the appellant appeared at the top of the lists of employees who had downloaded the most files to external devices: 91'982 files (182.8 GB), including 54'800 work files (approximately 85 GB), downloaded notably on 6-7 September 2015. The company's directives (22 October 2014 on information security, 20 May 2015 on the use of computers and messaging, and an undated directive on external devices) prohibited mass downloads or downloads of sensitive data without authorisation.

Hearings : Heard on 1 October 2015, the appellant admitted the download, which he presented as a backup of his M drive containing personal photos, and acknowledged that he had not requested authorisation. He was suspended the same day with immediate effect. He was then totally unfit for work from 2 October 2015. At the second hearing on 6 October 2015, he admitted having also downloaded the "presentation" folder of the shared R drive, citing retrospective work over five years, then mentioned holiday plans to work on the presentation; these explanations varied over the course of the proceedings.

Dismissal : On 9 October 2015, the company dismissed the appellant with immediate effect, for recent downloading activity constituting a serious breach of several directives, and a risk of damage and liability towards third parties. The letter, received on 13 October 2015, was sent by registered mail after he refused to sign. An undated final audit report concluded that there was no valid professional justification and that sensitive information was present, which could constitute a risk.

Cantonal proceedings : On 24 March 2016, the appellant brought an action before the Geneva Employment Tribunal, claiming in particular approximately CHF 4.66 million (salaries, holiday pay, an indemnity within the meaning of art. 337c para. 3 CO and damages) and a detailed certificate of employment. On 20 December 2017, the tribunal ordered the amendment of the certificate and dismissed the other claims. On 3 June 2019, the Employment Chamber of the Geneva Court of Justice dismissed the appeal, finding a real and valid serious cause, a reaction that was not belated, and the possibility of terminating immediately even during a period of protection against dismissal.

Appeal to the Federal Supreme Court : The appellant principally seeks annulment of the judgment and remittal to the cantonal court; in the alternative, he resumes his pecuniary claims, except the claim for moral damages, and requests evidentiary measures. The respondent seeks dismissal of the appeal.

Considerations

Admissibility and scope of review : The civil appeal is admissible in principle (minimum amount in dispute of CHF 15'000, art. 74 para. 1 let. a FSCA; time limit under art. 100 para. 1 FSCA). The preliminary requests seeking production of documents by the opposing party are inadmissible as new (art. 99 para. 2 FSCA) and run up against the prohibition on new evidence (art. 99 para. 1 FSCA). The Federal Supreme Court rules on the basis of the facts established by the cantonal court (art. 105 para. 1 FSCA) and corrects only findings that are manifestly inaccurate, that is, arbitrary (art. 105 para. 2 FSCA). The appellant, who restates the facts over about ten pages as in a statement of claim, does not satisfy the strict principle of allegation (art. 106 para. 2 FSCA); his allegations are not taken into consideration.

Procedural complaints : The cantonal court's refusal to admit exhibits 132 and 133 as so-called improper nova does not breach art. 317 para. 1 CPC. It is for the party invoking such nova to show that it exercised the required diligence (art. 317 para. 1 let. b CPC), which the appellant did not do on appeal. The refusal to order the production of additional documents violates neither art. 316 CPC nor art. 8 CC: the cantonal court held that these documents were irrelevant or that the file allowed an anticipatory assessment of the evidence. Only arbitrariness could be invoked, which the appellant does not do.

Serious cause within the meaning of art. 337 CO : Immediate termination is an exceptional measure, applied restrictively. Only a particularly serious breach, objectively capable of destroying the relationship of trust or of affecting it so deeply that continuation of the employment relationship cannot be required, may justify it (art. 337 paras. 2 and 3 CO). The judge assesses freely, considering the employee's position, the nature and duration of the relationship, and the seriousness of the breaches. The reason for dismissal is a question of fact, while whether it constitutes serious cause is a question of law. Termination must occur without delay: a deliberation period of two to three working days is in principle accepted, with possible extensions justified by practical requirements, and the period does not start to run while the extent of the breaches has not been established.

Reason for dismissal and absence of arbitrariness : The reason retained by the cantonal court, namely the downloading of a considerable volume of confidential data to a private external medium, without authorisation or professional justification, in breach of the directives, is not arbitrary. The dismissal letter and the respondent's answer rely on the same reason. The argument that the reason was clarified late or was replaced by the accusation of theft of 7 October 2015 is rejected. The findings that there was no incompatibility of temperament as a real reason are not arbitrary.

Reality of the breaches : The downloading of 54'800 work files constitutes without doubt a mass download within the meaning of the directive of 20 May 2015, even taking…