top of page

The admissibility of evidence obtained illegally or unfairly

It is important first of all to define the principle of admissibility/admissibility of evidence.

The principle of admissibility of evidence is a legal concept that concerns the admissibility of evidence in court. It sets out the rules and criteria that determine whether particular evidence can be presented and considered by the court in legal proceedings. This principle aims to ensure the fairness and reliability of the judicial process by limiting the type of evidence that can be submitted to the court for consideration.

Riviera Private Investigation, private detective firm, Nice

The rules for admissibility of evidence vary from one legal system to another, but certain general trends are often present. Here are some principles commonly associated with the admissibility of evidence:

  • Relevant and Relevant: The evidence must be relevant to the ongoing dispute. This means that they must have a direct link to the facts or issues in dispute.

  • Not Illegal or Immoral: Evidence obtained illegally or immorally, such as through violations of constitutional rights, may be excluded. This is intended to deter misconduct in the collection of evidence.

  • Reliability: Evidence must be reliable and credible. Questionable evidence or evidence based on unreliable sources may be excluded.

  • Compliance with Procedural Rules: Evidence must be presented in accordance with the procedural rules established by the court. This may include rules on how witnesses are questioned, how documents are introduced, etc.

  • Legal Presentation: Evidence must be presented in a legal manner, respecting procedural rules and avoiding inappropriate behavior.

The overall objective of these rules is to ensure that evidence presented in court is reliable, relevant and fairly obtained, thereby contributing to fair and equitable decision-making. Lawyers have a responsibility to ensure that the evidence they present meets these admissibility criteria.

Until recently, in the context of an action before civil courts (e.g. Judicial Court), evidence obtained illegally or unfairly was systematically excluded, because it was deemed inadmissible. Evidence obtained illegally or unfairly was equivalent, for example, to evidence obtained as part of clandestine recording (i.e. without the person recorded being informed of the recording), or following a stratagem/manipulation.

The Court of Cassation recently decided otherwise (end of December 2023), as part of a decision (also called “ Arrêt ” ) of its plenary assembly, thus establishing what is called a reversal of jurisprudence.

A reversal of jurisprudence, also called a reversal of jurisprudence, occurs when a court decides to change its position on a specific legal issue. In other words, it is a radical change in a court's interpretation or application of the law from its previous decision on the same subject.

The legal system often relies on stability and predictability, but courts may reconsider and change their legal interpretations over time. Reversals in jurisprudence can result from new information, new perspectives, changing social norms, or even the changing composition of courts.

When a reversal in case law occurs, it often has a significant impact on how the law is applied in similar situations in the future. It may also influence other courts dealing with similar issues, as they may be required to follow the new direction established by the reversal of case law.

In this case, the Court of Cassation now accepts that, in a civil dispute, a party can use, under certain strict conditions, evidence obtained unfairly to assert its rights.

This is particularly the case for an employer in a lawsuit contesting by the employee a dismissal for serious misconduct.

Here, the plenary assembly of the Court of Cassation follows a precise argument :

The Court of Cassation admits that unfair means of proof can be presented to the judge as long as they are essential to the exercise of the litigant's rights. However, taking this evidence into account must not cause a disproportionate attack on the fundamental rights of the opposing party (privacy, equality of arms, etc.)

« Thus, it must be considered that, in a civil trial, illegality or disloyalty in obtaining or producing a means of proof does not necessarily lead to to exclude him from the debates. The judge must, when asked, assess whether such evidence undermines the fairness of the procedure as a whole, by balancing the right to proof and the conflicting rights present, the right to proof being justify the production of elements infringing other rights provided that this production is essential to its exercise and that the infringement is strictly proportionate to the aim pursued 

This solution constitutes a reversal of jurisprudence. It is inspired by the case law of the European Court of Human Rights. It responds to the need not to deprive a litigant of the possibility of proving his rights, when the only proof available to him presupposes, in order to obtain it, an infringement of the rights of the opposing party.

The decision of the Court of Appeal, which dismissed the clandestine recordings on the grounds that they had been obtained unfairly, is censored.

The case is sent back to another court of appeal. This will have to verify on the one hand, that the recordings were essential to prove the serious misconduct of the employee, on the other hand, that the use of these recordings made without the employee's knowledge does not cause a disproportionate harm to his fundamental rights.

Before this judgment, in civil matters, the Court of Cassation considered that evidence collected by unfair means should be declared inadmissible.


In its decision of December 22, 2023 (appeal no. 20-20.648), it adds some measure to this principle by using the terms "does not necessarily lead to excluding it from the debates"._11100000-0000 -0000-0000-000000000111_


The impact of this court decision does not relate to the characterization of the disloyalty of the means used, but to the possibility of admitting an element of evidence provided by such a means.



bottom of page