New developments regarding the admissibility of an unlawful means of evidence

The Court of Cassation has just issued a very important decision for employers on the law of evidence, which for several years has been based on a principle of loyalty established by case law.
Evidence obtained without the knowledge of the person concerned through a maneuver or stratagem was indeed declared inadmissible by the lower courts (Cass, Ass Plén., 7 January 2011, No. 09-14.316).

Such a limitation in the administration of evidence has given rise to significant litigation before the European Court of Human Rights, which in several judgments has recognized a principle of balancing the applicants' right to respect for their private life against the employer's interest in protecting its rights. Thus, on the basis of Article 8 of the European Convention on Human Rights, it has been able to admit unlawful evidence to justify the dismissal of employees, such as video surveillance without prior information to employees in order to prove theft. (ECHR 17 October 2019, 1874/13).

Under the influence of European case law, the Court of Cassation took a first step three years ago toward the admissibility of unlawful or disloyal evidence. In a ruling of September 30, 2020, it recognized that evidence infringing on an employee's privacy should not necessarily be excluded from proceedings, provided it was proportionate to the pursued goal and defended the employer's legitimate interest. (Cass, soc September 30, 2020, n°19-12.058).

After several decisions in the same vein (Cass soc 25 November 2020 n°17-19.523; Cass, soc 10 November 2021 n°20-12.263), the Court of Cassation has just made a definitive reversal.

By two rulings of December 22, 2023 (Ass. Plén., December 22, 2023 n°20-20.648 and n°21-11.330), the Court of Cassation held that “it is now appropriate to consider that, in civil proceedings, the unlawfulness or unfairness in obtaining or producing evidence does not necessarily lead to its exclusion from the debates.”

In doing so, it admitted that transcripts of clandestine recordings of interviews with the employee by the employer could be used to provide evidence of the employee's misconduct and consequently justify their dismissal.

This decision was nevertheless preceded by the reminder that evidence obtained without the person's knowledge or obtained by a maneuver or stratagem is inadmissible, on the grounds that justice must be rendered fairly: "The judge must, when requested, assess whether such evidence undermines the fairness of the proceedings as a whole, by balancing the right to evidence and the conflicting rights at stake, the right to evidence being able to justify the production of elements affecting other rights provided that this production is essential for its exercise and that the interference is strictly proportionate to the aim pursued."

This ruling opens interesting perspectives for the employer, who can now, within the judicial framework, submit evidence obtained without the employee's knowledge. However, it must bear in mind that such documents may be retained only if they are essential for establishing the truth and if the infringement of other rights (particularly respect for private life) is strictly proportionate to the pursued objective.

Ultimately, it is now for the judge to admit unlawful or disloyal evidence only in the event that no other evidence can enlighten him or resolve the dispute.

Corporate law