According to Article L4121-1 of the French Labour Code, the employer is required to take the necessary measures to ensure the safety and protect the physical and mental health of his salaries.

Thus, he must prevent acts of moral or sexual harassment and react in a way that makes them stop as soon as they appear.

It is increasingly common for the employer, upon receiving a report of harassment, to conduct an internal investigation in order to fulfil their duty of care to employees.

The internal investigation is also conducted for evidentiary purposes. It serves to prove the misconduct of an employee dismissed for harassment and will also be used in case of a claim issues by the employee. 

The question arose as to whether an internal investigation was necessary to prove the misconduct of an employee accused of harassment. 

In a ruling of January 14th, 2026 (Cass.soc.14-1-2026 no.24-19.544), the Court of Cassation clearly reiterated the principle of freedom of proof in employment law matters and the absence of an obligation for the employer to conduct an internal investigation in the event of a report of sexual harassment. 

This ruling provides an opportunity to recall that:

• An internal investigation is not mandatory in cases of denunciation of sexual or moral harassment, in accordance with the principle of freedom of proof.

In this case, the employer, to justify the dismissal, provided statements from a victim, her complaint to the police, and various employee attestations stating they had heard her confidences shortly after the events, as well as the report from the psychologist who had seen her.

The Court of Appeal had deemed these elements insufficient, as the employer had not considered an internal investigation that could corroborate the victim's claims about the employee's behaviour.

The Court of Cassation recalls that no provision of the Labour Code requires the employer to conduct an internal investigation in the event of a report of sexual harassment and that it was therefore up to the judge to assess the value and scope of the submitted evidence. 

This jurisprudence aligns with previous case law according to which as long as the employer has taken sufficient measures to preserve the employee's health and safety, the absence of an internal investigation does not constitute a breach of the employer's duty of care (Cass. soc., 12 June 2024, no. 23-13.975).

In this case, the employer had responded to the employee's alerts and had reacted quickly by taking a stance on disputes between her and her colleague, and a second time, by responding to her questions and providing clarifications.

However, in that case, the facts of moral harassment were not established, and it was debatable whether the absence of harassment led the Court of Appeal to rule that the employer's email responses to the employee's queries were sufficient. This jurisprudence therefore remained to be confirmed, which has now been done.

While an internal investigation is not mandatory, it remains a useful process for gaining a complete understanding of the facts and taking appropriate measures. However, it will be up to the employer, depending on the situations they face, to decide whether it is appropriate to conduct an internal investigation.

• The internal investigation is one piece of evidence among others, the probative value of which is for the lower courts to assess.

Organising an internal investigation does not in itself constitute an absolute guarantee of proof.

Indeed, the lower courts must assess the probative value of an investigation which is often contested by employees before the courts. 

Thus, it was recently ruled that doubt benefited the employee even though an internal investigation had been conducted following reports of moral harassment. 

In this case, the Court of Appeal had noted that: 

• some interview reports were truncated and did not establish that the person interviewed had personally witnessed the events;
• some of the alleged facts against the employee were not corroborated by other evidence, even though they allegedly occurred in front of witnesses, according to the interview reports, in which several names had been censored;
• the entirety of the investigation was not submitted to the court, with only 5 interview reports out of 14 conducted. The employer justified this by the desire to respect the anonymity of certain employees, without explaining why these elements could not have been anonymised. For the Court, nothing allowed to exclude that these reports were suppressed due to their favourable nature to the accused employee. 

It should be noted that the employer argued that proof was free, which allowed them to communicate all or part of the investigation report. They also considered that they could, in the name of respecting employees' private and personal lives, exclude certain passages at their request (Cass. soc., 18 June 2025, no. 23-19.022)

Conversely, the probative value of an investigation into alleged harassment was recognised when: 

• the employer had not interviewed all employees who were witnesses or involved in the disputed events,
• the two employees who reported the events had been interviewed together,
• the interview reports were not signed,
• the duration of the interview with the employee accused of harassment had not been specified,
• employee representatives had not been consulted.

(Cass. soc., 29 June 2022, no. 21-11.437). 

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In conclusion, this ruling of January 14th, 2026 (Cass.soc.14-1-2026 no.24-19.544) confirms that an internal investigation is not mandatory in cases of denunciation of moral or sexual harassment and that it does not in itself constitute an absolute guarantee of proof.

Nevertheless, it will be necessary to remain attentive to jurisprudential positions on the probative value of investigations in order to implement appropriate processes. 

The Defender of Rights has, in this regard, recently published a detailed methodology to help employers conduct such investigations (Framework Decision of the Defender of Rights 2025-19 of 05-02-2025).

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