Sentence Review Under LO 1/2026: Applying the More Favorable Criminal Law in Spain

The entry into force of Organic Law 1/2026 on 10 April 2026 has amended the Spanish Criminal Code in offences that come up very often, such as theft in its repeat-offender forms, fraud and the theft of mobile phones. When a reform of this kind lowers the penalty for an offence, an immediate question arises for anyone already convicted of those facts: can they benefit from the new law even though their sentence is final and they are serving it? Under Spanish law the answer is yes, where the new rule turns out to be more favorable. As criminal defence lawyers who handle sentence reviews under LO 1/2026, we explain in this guide what the principle of favorable retroactivity means, which sentences can be reviewed, how the penalty is compared and what the procedure looks like.

The Principle of Retroactivity of the More Favorable Criminal Law

The starting point is a safeguard with constitutional footing. Article 9.3 of the Spanish Constitution declares that punitive provisions which are unfavorable or restrict rights cannot operate retroactively. Read the other way round, that same provision underpins the opposite rule: favorable criminal provisions do apply retroactively. What is harmful cannot look backwards; what benefits the person can.

Article 2.2 of the Criminal Code spells this out without ambiguity: criminal laws that benefit the offender have retroactive effect even if, when they come into force, a final judgment has already been handed down and the person is serving the sentence. It is one of the few real exceptions to the force of res judicata: the finality of the judgment does not prevent a later, more lenient law from reaching a sentence that is already being enforced.

What Changes With LO 1/2026

LO 1/2026 is not a wholesale overhaul of the Criminal Code but a selective amendment of certain offences and sentencing rules. The areas affected include:

• Theft, with changes to the repeat-offender regime that may alter the applicable penalty in cases of reiteration.
• Fraud, in aspects of its sentencing framework and the circumstances that shape it.
• The theft of mobile phones, which receives specific treatment.

Not every reform is automatically more favorable. A review only lies where, applied to the specific case, the new rules produce a more lenient sentencing outcome than the final judgment. The defence's first task is therefore a technical, case-by-case analysis of whether the convicted person genuinely falls within one of the improvement scenarios.

Which Sentences Can Be Reviewed

The mechanism reaches both final sentences awaiting enforcement and sentences actively being served, even at an advanced stage. There are three essential requirements:

• A final judgment handed down under the previous law, whether already being enforced or yet to be enforced.
• A later, more favorable rule: LO 1/2026 must be objectively more beneficial for the convicted person in their specific case, not in the abstract.
• An application: the review does not operate by itself; it must be requested and decided in an incidental proceeding.

No review lies where the penalty imposed also fits within the new framework — because the judge could equally have imposed it under the new law — or where the change affects only a part of the penalty range (for example the maximum) that has no bearing on the specific penalty actually fixed in the judgment.

Comparing the Penalties as a Block

A decisive technical point is how the old law is compared with the new one. The rule, settled in Spanish Supreme Court doctrine on earlier reforms, is that the comparison is made as a block and not provision by provision. In other words, the overall sentencing result that each set of rules would produce — taken as a whole, with its basic offence, its sub-types, its aggravating factors and its sentencing rules — must be weighed, and the more favorable one applied in full.

An important consequence follows: you cannot build an "à la carte" regime by taking the most beneficial parts of the old law and the most beneficial parts of the new one. When the more favorable set of rules is chosen, it applies in its entirety, with its advantages and any trade-offs. The defence's job is precisely to show, with the numbers of the case, that the new body of rules leads to a lower penalty.

An abstract example helps. If the final judgment imposed a penalty at the bottom of the range for the offence applied and LO 1/2026 lowers that minimum, the comparison usually favours the convicted person, because under the new law the court could not have imposed so high a penalty. By contrast, if the penalty imposed sits comfortably within the new framework — so that the judge could equally have set it under the reform — the review does not lie, even if the new law "sounds" more lenient. What matters is not the wording of the provision in the abstract, but the concrete result for the penalty already imposed.

This way of comparing is not a recent invention: it reflects doctrine long settled by the Spanish Supreme Court in the wake of earlier reforms and recorded in agreements of its Criminal Chamber, which on each major legislative change has spelled out how sentences under enforcement are to be reviewed. The defence relies on those criteria to frame the case correctly from the very first submission.

The Review Procedure

The review is dealt with in an incidental proceeding with a clear structure:

• An application to the sentencing court by way of a reasoned submission, with the side-by-side analysis of the previous rules and those of LO 1/2026 applied to the case.
• A hearing of the public prosecutor and of the convicted person, which is an essential safeguard of the procedure.
• A decision by reasoned order in which the court decides whether to review the sentence and, where appropriate, fixes the new penalty.
• A fresh sentence calculation and, where relevant, an update of the prison file to reflect the revised penalty.

The order resolving the review can be appealed under the terms the procedural law provides depending on the court that issued it. If the court refuses the review without properly weighing the greater leniency of the new rule, that refusal can be challenged; hence the importance of a well-built initial submission that closes off the comparative analysis.

Effects on Enforcement and Prison Benefits

A favorable review does not stop at lowering the figure of the sentence: it produces knock-on effects on enforcement. As the total penalty is reduced, the periods measured against it are recalculated:

• Access to leave permits and other variables that depend on time served.
• Progression to open conditions (third grade) and, where applicable, parole, whose timelines are projected onto the new penalty.
• Any consolidation or accumulation of sentences, if the reduction alters the calculation of the maximum enforcement limit.

The most drastic effect is immediate extinction: if the time already served equals or exceeds the new sentence, the penalty can be declared served at once. That is why a good review submission does not merely request the new penalty but expressly sets out each favorable collateral consequence, so the enforcement court reflects it in the file without delay.

Common Mistakes and Cautions

Sentence review looks straightforward on paper, but in practice it concentrates several risks. A few cautions are worth keeping in mind:

• Assuming the reduction is automatic. It is not. Without a reasoned application, a reduction you are entitled to may never arrive, or arrive late.
• Confusing abstract leniency with concrete leniency. The reform sounding more lenient is not enough: you have to show that, with the numbers in the judgment, the result is lower.
• Overlooking the prison effects. Limiting yourself to the new penalty without requesting the recalculation of timelines leaves much of the benefit untapped.
• Neglecting the deadline and the route of appeal against a mistaken refusal.

Each of these points justifies careful technical handling: what is at stake is not a procedural nicety but the actual time of deprivation of liberty.

Where to Find Specialist Assistance

Alonso Sala is a firm dedicated exclusively to criminal law, based at Calle Velázquez 27, Madrid, with coverage across the whole of Spain. We assess whether a final sentence can benefit from LO 1/2026 as the more favorable law, prepare the review application before the sentencing court and set out the effects on enforcement and prison benefits. If you or a relative is serving a sentence that might be affected by the reform, it is advisable to analyse the case as early as possible so as not to delay a reduction you may be entitled to.