Building an evidence file for the family court judge

Before the family court judge (juge aux affaires familiales, JAF), everything turns on facts: each parent's availability, the child's living conditions, everyone's resources, the reality of this or that behaviour. A well-built file — factual, dated, orderly — helps the judge decide with full knowledge of the case. Here, in a documentary way, is how evidence works in family matters and what material to gather.

In civil matters, evidence is free

To prove a fact (a situation, a behaviour, a lack of contribution…), the law sets out a simple principle. Article 1358 of the Civil Code states:

"Except in cases where the law provides otherwise, evidence may be adduced by any means."

In other words, before the JAF, most of what one seeks to establish concerns facts and can be proved by any means: witness statements, messages, official reports, documents. (The rule is different for proving a legal act such as a contract, where a written document is in principle required above 1,500 €.)

The useful forms of evidence before the JAF

On testimony in particular, see our dedicated guide: The witness statement (Article 202 CPC).

Police log entry or complaint?

The two are often confused. The police log entry (main courante) is a mere declaration recorded by the police or gendarmerie: it dates your statements but does not trigger prosecution. A complaint (plainte), by contrast, brings the matter before the public prosecutor. In both cases it is a declaration: it places the facts in time but does not prove them on its own — it acquires its value within a body of evidence.

The report by a commissaire de justice

The commissaire de justice (the profession that merged the huissiers de justice and the judicial auctioneers) may draw up an official report. Their purely material findings stand as proof until the contrary is shown. This is useful for objectively freezing a situation at a given moment.

The fairness of evidence: a principle to know

You cannot prove things by any means. The right to respect for private life (Article 9 of the Civil Code) and the confidentiality of correspondence set limits: the other person's diary, mailbox or phone are not at your disposal.

Case law has evolved on this point. For a long time, evidence obtained unfairly (for example a recording made without the person's knowledge) was inadmissible as a matter of principle. In a ruling of the Full Court (Assemblée plénière) of 22 December 2023 (No. 20-20.648 and No. 21-11.330), the Cour de cassation held that, in a civil trial, evidence obtained unlawfully or unfairly need not necessarily be set aside: the judge balances the right to evidence against the rights at stake (private life, confidentiality of correspondence), the evidence being admissible only if its production is indispensable and the interference strictly proportionate to the aim pursued.

⚠️ To be read with caution. This is not a blank cheque. Unfair evidence is admitted only exceptionally, case by case, under this twofold review. Above all, obtaining evidence unlawfully remains reprehensible in itself: recording or filming someone without their knowledge, accessing their phone or mailbox, geolocating them, can constitute a separate criminal offence (invasion of privacy, breach of the confidentiality of correspondence) and engage your liability — irrespective of the question of evidence. The safe rule: gather fair material, and touch the other person's private life only with the greatest restraint.

What the judge examines

The JAF rules notably on the child's residence, the contact and accommodation rights, parental authority and the contribution to the child's maintenance and education (child maintenance).

Two textual markers:

• The contribution is set "in proportion to the resources of each parent and to the child's needs" (Article 371-2 of the Civil Code) — hence the importance of producing complete financial supporting documents from both sides. On its amount, its revision and its recovery, see our guide Child maintenance.
• The judge "settles the questions submitted […] while taking special care to safeguard the interests of minor children" (Article 373-2-6 of the Civil Code). The best interests of the child are the paramount consideration (Article 3 of the International Convention on the Rights of the Child).

A useful file is therefore not an indictment of the other parent: it is a set of concrete material that sheds light on these questions.

The method: a clear, dated timeline

Beyond the documents themselves, it is the organisation that makes a file readable:

• Record the facts as they occur, dated, factual, without interpretation — memory degrades and dates quickly blur together.
• Gather each document in the right place and number them so you can refer back to them.
• Build a timeline: a sequence of dated and sourced facts is far more convincing than a general recollection — our guide Keeping a timeline of events sets out the method.
• Distinguish what you saw, what a third party observed, and what you assume.

This is precisely the underlying work — keeping a dated log of facts, gathering your documents, preparing your questions for a professional — that Aridelle is designed to make easier. And once the file is ready, it remains to refer the matter to the judge: our guide Applying to the family court judge sets out the procedure.

Further reading

• What are the forms of evidence in a civil trial? (service-public.gouv.fr, F1800)
• Child maintenance: what are the differences with the compensatory allowance? (F2236)
• Press release from the Cour de cassation on unfair evidence (22 December 2023)