Medicine is not an exact science, and its practice and application in daily life are not free from risks or the commission of errors. Therefore, Spanish law provides several avenues for claims in cases of malpractice, mishandling, or lack of diligence in medical procedures.

The available legal avenues are criminal, civil, and administrative law.

The criminal route is reserved for the most flagrant and obvious cases, where the failure to apply basic knowledge to a specific case has caused very serious harm to the patient (including death). Criminal liability is only applicable in the most severe cases of illegality, as this jurisdiction only acts as a last resort to punish inappropriate actions. For a medical act to give rise to criminal liability as a crime, it must meet the following requirements:

1. a) Human Conduct: The act must be performed by a human through action or omission. A doctor cannot be held criminally responsible for a mechanical or electronic failure, although civil liability may arise.
2. b) Unlawfulness: The act must be contrary to a legal norm.
3. c) Codification as a Crime: The act must be defined as a crime within the Criminal Code.
4. d) Intentional or Reckless Conduct: The act must be performed with recklessness or intent. Most cases involve reckless conduct, as deliberate crimes are uncommon given that healthcare professionals aim to heal. The perpetrator must also be imputable and capable of being held responsible for their actions.
5. e) Punishable Conduct: There must be a penalty associated with the committed crime.

Civil liability involves answering for harm caused by fault or negligence, as regulated by Article 1902 of the Spanish Civil Code. The existence of malpractice forms the basis for any damages claim for medical negligence. This means that the healthcare professional did not act according to appropriate protocols and practices. However, there are situations where professionals face unclear circumstances and act based on their own judgment. In such cases, proving negligence is more challenging and requires comparing their actions with what other professionals would have done in the same situation.

To establish civil liability, the following must be present:

1. a) Malpractice: The professional acted differently than how other colleagues would have acted.
2. b) Harm: The professional’s actions caused physical and/or psychological harm to the patient or undesirable consequences.
3. c) Causality: A direct causal relationship between the healthcare professional’s irregular conduct and the harm caused to the patient.

In the context of the administrative jurisdiction, the viability of the administration’s liability requires the unlawfulness of the result or injury whenever there is a causal link between the normal or abnormal functioning of the public service and the harmful or injurious outcome. For medical or healthcare-related liability, the existence of an injury alone is not sufficient—it requires examining the "Lex Artis" to determine the correct medical conduct, irrespective of the outcome on the patient's health or life, as neither science nor the administration can guarantee patient health or recovery in all cases.

In the Spanish Supreme Court ruling of December 21, 2020 (RC 803/2019), it is reiterated that the unlawfulness of the result or injury—stemming from a breach of the Lex Artis—is crucial for declaring patrimonial liability attributable to the Administration. Therefore, it is necessary to prove its occurrence. To summarize, in its sixth Legal Ground, the Court indicates: As this Chamber and Section have declared, in judgments of September 30 and September 13, 2002, and in the repeated rulings of this Supreme Court, including the judgment of June 5, 1998, the provision of a particular public service by the Administration and the ownership of the material infrastructure for its provision do not imply that the current system of objective patrimonial liability of Public Administrations turns them into universal insurers of all risks, aimed at preventing any unfavorable or harmful eventualities for citizens that may arise independently of the administrative action. Otherwise, as the appellant contends, it would transform it into a providential system not contemplated in our Legal Order. The Court further adds: Even though the liability of the Administration has been classified by the Jurisprudence of this Chamber as a case of objective liability, it does not mean that the Administration is responsible for all harmful outcomes that may occur merely from the use of public facilities. As previously mentioned, it is necessary that these damages are the direct and immediate consequence of its normal or abnormal functioning. This means that there must be the existence of an unlawful damage, a causal relationship, and the fact that the citizen is not obliged to endure the aforementioned damage.