Means of evidence: admissibility of unfair evidence and anonymous testimony before French employment Tribunals

1. Possibility to take unfair evidence into account

In civil matters, case law has long refused to take into account evidence obtained unfairly, such as recordings made by employees or employers without the agreement of the other party, despite some adaptations with this rule in recent years.

Since a ruling by the plenary assembly of the French Supreme Court on 22 December 2023 (French Court of Cassation. Ass plén., 22 December 23, no. 20-20648), the Court of Cassation now generally accepts that a party to a dispute may use unfairly obtained evidence to assert their rights in a civil lawsuit.

However, this admissibility remains conditional.

When requested to do so, the judge must assess whether such evidence undermines the fairness of the proceedings as a whole, weighing up the right to evidence against the conflicting rights at stake, as the right to evidence may justify the production of evidence that infringes other rights, provided that such production is essential to the exercise of that right and that the infringement is strictly proportionate to the aim pursued.

Consequently, the judge must assess:

• the relevance of the evidence in relation to the rights of the parties involved and its necessity, in particular in view of the absence or insufficiency of other evidence;

• the negative impact of the evidence on the interests of the other party. The judge must therefore verify whether, in view of the interests at stake, the infringement linked to the unfairness of the evidence is not disproportionate.

The Court has thus accepted the principle of the admissibility of evidence obtained unfairly by the employer, such as:

• • recordings made using a hidden video surveillance device to reveal thefts committed by an employee in the context of missing stock;
  • audio recordings of an employee who expressly refused to provide his employer with a record of his commercial activity;
  • personal emails intended to prove that the employee disclosed highly confidential technical and commercial data to a third-party company;
  • the contents of USB sticks opened by the employer and found in an employee’s office.

In the case of evidence obtained unfairly by an employee in the context of moral harassment, clandestine recordings were dismissed because there was other evidence provided by the employee that was sufficient to suggest harassment (the regime of evidence regarding harassment is simplified before the French employment court). In another case, such recordings were admitted by the judge because their production was deemed essential to the right of evidence. For example, a recording demonstrating pressure exerted by the employer on an employee to accept a contractual termination was admitted.

While these developments in case law may enable employers to gather evidence of misconduct by their employees in circumstances where such evidence was previously difficult to obtain in practice, they should also encourage employers to be particularly vigilant in their conversations and comments, especially in the following situations:

• during performance reviews, in particular where the employee is not performing at the expected level;
• during the pre-dismissal meeting, where the employee may wish to demonstrate that the interview deviated from its purpose, or even that the employer verbally informed them of their dismissal without waiting for the legal cooling-off period;
• during termination negotiations, where the employee may wish to establish any pressure that may have been exerted on them or simply obtain confirmation that the employer has no serious grounds for dismissing him or her.

Employers should therefore also be extra vigilant in view of the broader admissibility of unfair evidence, in particular when they are in the process of implementing sanctions or terminating an employment contract, or more broadly in the context of tension with an employee.

2. Taking anonymous testimony into account

The Court of Cassation had previously ruled that while, in principle, a judge cannot base their decision solely or decisively on anonymous testimony, they may nevertheless take into consideration anonymised testimony (i.e. rendered anonymous in order to protect their authors, but whose identity is known to the party producing them) when other elements are brought into the proceedings to corroborate this testimony and enable the judge to analyse its credibility and relevance.

In a ruling dated 19 March 2025 (Cass. soc. 19 March 2025 No. 23-19.154), the Court of Cassation went further and allowed the consideration of exclusively anonymised testimony under certain conditions.

In the absence of evidence supporting or corroborating such testimony, it is up to the judge, in a civil trial, to assess whether the production of testimony whose author’s identity is not disclosed to the person against whom the testimony is used undermines the fairness of the proceedings as a whole, by balancing the principle of equality of arms and the conflicting rights at stake.  the right to evidence may justify the production of evidence that infringes the principle of equality of arms, provided that such production is essential to its exercise and that the infringement is strictly proportionate to the aim pursued.

In this case, the judge had to weigh up:

• the rights of the dismissed employee and the principles of equality of arms and adversarial proceedings, on the one hand
• the employer’s obligation to protect the health and safety of its employees, in accordance with Articles L. 4121-1 and L. 4121-2 of the Labour Code, on the other.

In this case, the Court accepted a bailiff’s collection of anonymous testimonies attesting to the dismissed employee’s aggressive behaviour towards certain employees, manifested in threats, derogatory remarks, intimidation and violent language.

The Court of Appeal’s ruling was therefore overturned, and the case was referred to another court, which will have to re-examine whether the dismissal for gross misconduct was justified, including the anonymous employee testimony in the proceedings.

This ruling now allows employers to offer additional protection to employees who would have not dared to testify because of fear of reprisals or tensions, especially in the context of investigations about harassment.

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