The dies a quo in medical liability: uncertain diagnosis, stabilisation of the sequelae and limitation after Supreme Court Judgment 182/2026
Judgment 182/2026 of 10 February of the “Tribunal Supremo” —Spain's Supreme Court— strengthens the case law on when time begins to run for limitation purposes in medical negligence claims where the diagnosis and the extent of the sequelae remain uncertain for years. In a case of neurological injury to a minor, the medical reports spoke of a “possible” or “probable” diagnosis or of a “suspected” one, and definitive confirmation came later. The Court insists on the principle actio nondum nata non praescribitur: limitation does not begin to run until the injured party has sufficient material genuinely to know the nature and the extent of the harm. It also stresses that the party relying on limitation must clearly establish the dies a quo and that doubts are not to be resolved to the detriment of the injured party, which is of particular importance in neurological injury in children, progressive harm, sequelae that take time to stabilise and subsequent official recognitions of disability.
1.The case: childbirth, neurological injury and the dispute over the start of the limitation period
STS 182/2026, a judgment of the “Tribunal Supremo”, Spain's Supreme Court, determines a cassation appeal in a matter of civil liability for medical malpractice during childbirth, the claim being brought against the insurer of the “Servicio Andaluz de Salud”, the Andalusian health service. The parents of a minor, in their own name and on her behalf, claimed damages for the harm arising from the obstetric care given in 2005. The child had severe neurological sequelae, but the definitive diagnosis of the condition and of its extent took shape over the years.
The court of first instance dismissed the claim, finding it barred by limitation and applying the one-year period laid down in article 1968 of the “Código Civil” —the Spanish Civil Code— for non-contractual liability. It took the view that, although the sequela was permanent, the claimants had become aware of the harm and of its extent in March 2016, the date of a significant medical report, and that, by the time the out-of-court claim was made in June 2017, the year had elapsed. The “Audiencia Provincial”, the provincial appeal court, upheld the judgment in its entirety, maintaining the finding of limitation and declining to address other questions, such as the cover provided by the insurance policy.
The Supreme Court allows the claimants' cassation appeal, sets aside the judgment and declares that the claim was not barred by limitation, remitting the case to the provincial appeal court so that it may rule on the merits. Everything turns on the determination of the dies a quo for limitation purposes in a context of uncertain diagnosis and of progressive neurological sequelae.
2.The principle actio nondum nata non praescribitur and article 1969 CC
STS 182/2026 relies on article 1969 of the Civil Code, which provides that time for the limitation of every class of action, where there is no special provision determining otherwise, is to be counted from the day on which the action could have been brought. That provision has traditionally been construed as meaning that limitation does not begin to run while the right of action has not yet arisen, that is, while the injured party does not have the factual and legal material needed to bring it with sufficient knowledge of the matter. Hence the classic formulation of the principle actio nondum nata non praescribitur.
In the field of medical liability, that principle means that the limitation period does not start until the injured party knows, or may reasonably know, of the existence of the harm and of its nature, as well as of the possible causal link with the medical care provided. The mere occurrence of the harmful event is not enough; sufficient knowledge of the extent of the sequelae and of their stable or irreversible character is required.
In the case under examination, the medical reports issued over a period of years used expressions such as “possible”, “probable” or “suspected” to refer to the child's neurological diagnosis. Definitive confirmation, without reservations, of the diagnosis and of the extent of the sequelae came at a later point, which the Court takes as the reference for the start of the limitation period. While the diagnosis remained uncertain and the sequelae had not stabilised, the right of action could not be regarded as fully arisen for limitation purposes.
3.Uncertain diagnosis, stabilisation of the sequelae and the point of sufficient knowledge
STS 182/2026 carries out a detailed analysis of the medical reports and of the child's clinical course. It notes that, over a lengthy period, the doctors used terms of diagnostic uncertainty, such as a “possible” or “probable” neurological condition, or a “suspected” one, and that definitive confirmation of the diagnosis, clearly stating the nature and the extent of the sequelae, came at a later date, close to 2018.
The Court takes the view that, in that context, the dies a quo for limitation purposes cannot be placed at any point before the diagnosis and the sequelae have reasonably stabilised. Limitation, which is to be construed restrictively, cannot operate to the detriment of the claimant where there is doubt as to the moment at which the harm became settled and knowable in its true nature. The Chamber insists that sufficient knowledge of the harm is not reduced to the perception of symptoms or to the existence of provisional reports, but requires a degree of stability and of diagnostic certainty.
This approach is of particular importance in neurological injury in children and in progressive harm, where the child's development and the evolution of the sequelae may extend over years. The stabilisation of the sequelae, understood as the moment at which their permanent character and their functional extent can be asserted with reasonable certainty, becomes the reference point for the start of the limitation period. Subsequent official recognitions of disability, although they do not of themselves determine the dies a quo, may be significant indications of the moment at which the situation became settled and was recognised by the authorities.
4.The burden of proving the dies a quo and the resolution of doubts in favour of the injured party
STS 182/2026 stresses that the party relying on limitation must clearly establish the dies a quo. Limitation is a defence which benefits the defendant and which, by its nature, is to be construed restrictively. It is not enough to plead in general terms that the period has elapsed; it must be shown when it began to run, by identifying the moment at which the action could have been brought under article 1969 CC.
In the case under examination, the insurer and the health authority maintained that the period had started in March 2016, the date of a medical report which, on their reading, already reflected sufficient knowledge of the harm. The Supreme Court takes the view that that assertion has not been sufficiently established, in the light of the persistence of terms of uncertainty in the reports and of the subsequent diagnostic confirmation. Faced with doubt, the Chamber chooses not to act to the detriment of the injured party, applying the principle that limitation is to be construed restrictively.
The judgment emphasises that doubts as to the dies a quo are not to be resolved to the detriment of the injured party, particularly in contexts of complex and progressive harm. That line of reasoning strengthens the protection of patients and their families against rigid readings of limitation which might close off the route to a claim before the harm is fully knowable.
5.Practical significance: neurological injury in children, progressive harm and recognitions of disability
The doctrine of STS 182/2026 has significant practical implications in medical liability litigation. In the first place, in neurological injury in children, where the child's development and the evolution of the sequelae may extend over years, the moment at which the sequelae stabilise and the diagnosis is confirmed becomes the key reference point for the start of the limitation period. Medical reports using the terms “possible”, “probable” or “suspected” are not enough to fix the dies a quo; a diagnosis affirmed without reservations is required.
Secondly, in progressive harm, such as certain degenerative conditions or functional sequelae that worsen over time, it is essential to identify the moment at which the harm has become settled and its extent is reasonably knowable. Limitation cannot begin to run while the harm is still at a stage of uncertain evolution and the injured party does not have sufficient material to assess its nature.
Thirdly, official recognitions of disability, such as decisions assessing disability or “dependencia”, the Spanish long-term care status, may be significant indications of the moment at which the situation was recognised by the authorities, but they do not automatically determine the dies a quo. They must be analysed in conjunction with the medical reports and the clinical course, in order to determine whether they reflect that the harm has become settled or whether they are mere administrative milestones in a process that is still uncertain.
For litigation practice, STS 182/2026 means that, when analysing limitation in medical liability, it is essential to reconstruct the clinical and diagnostic chronology, to identify the moment at which the sequelae stabilised and to assess whether knowledge of the harm was sufficient. The burden of proof lies on the party relying on limitation, and doubts are to be resolved in favour of the injured party.
6.Conclusion: uncertain diagnosis, stabilisation of the sequelae and limitation in medical liability
STS 182/2026 consolidates and refines the case law on the dies a quo for limitation in medical liability where the diagnosis and the extent of the sequelae are uncertain. The principle actio nondum nata non praescribitur means that limitation does not begin to run until the injured party has sufficient material genuinely to know the nature and the extent of the harm, which, in neurological injury in children and in progressive harm, may occur years after the harmful event.
The judgment insists that the party relying on limitation must clearly establish the dies a quo and that doubts are not to be resolved to the detriment of the injured party. For litigation practice, the approach taken in STS 182/2026 calls for careful analysis of the clinical course, of the medical reports and of the recognitions granted by the authorities, and provides a solid basis for arguing that claims are not barred by limitation in contexts of uncertain diagnosis and of sequelae that take time to stabilise.
