Two co-defendants may share counsel even if one pleads guilty and the other does not

The joint representation of several defendants in the same criminal proceedings is a common and perfectly legitimate practice. The question of whether that unity of representation can be maintained when the defendants' positions diverge — particularly when one accepts the charge and the other contests it — is, however, one of the most sensitive issues in the right of defence. The Supreme Court judgment of 13 May 2026, issued in appeal 4799/2023, addresses it with practical criteria that are worth understanding.

The doctrine on joint defence of co-defendants

Spanish criminal procedure law does not prohibit several people charged in the same case from sharing a lawyer. Multiple defendants under a single legal representative are an everyday reality of criminal proceedings, and in many cases reflect a coherent defence strategy: the conduct charged, the interests and the positions of the defendants are substantially aligned.

The limit is set by a conflict of interest: where the defendants' positions are antagonistic, joint representation may become impossible or, at least, ethically compromised. The Supreme Court has, however, consistently stressed that a mere difference in stance is not the same as a real conflict. A conflict requires that the effective defence of one defendant directly and materially prejudices that of the other.

The guilty plea of one and the position of the dissenting defendant

The case before the Court raised a particularly delicate variation: one co-defendant decided to enter a guilty plea (conformidad), accepting the charge, while the other maintained their opposition and proceeded to trial. Does that split create a conflict of interest preventing joint representation?

The Supreme Court answers no — not automatically. The key lies in the legal scope of the guilty plea: what the pleading defendant admits is their own criminal liability, not that of the co-defendant. The guilty plea of one has no binding effect on the one who contests the charge. It cannot be used as incriminating evidence against the second defendant, nor does it serve to complete or supplement the evidence required to convict them.

The consequence is that the presumption of innocence of the non-pleading co-defendant remains intact. Any conviction must rest on independent, sufficient incriminating evidence, assessed autonomously. The pleading co-defendant's admission cannot substitute that requirement.

The criterion for detecting a real conflict of interest

The ruling offers a functional criterion for distinguishing a mere divergence of positions from the conflict of interest that prevents joint representation. The conflict is real when one defendant's defence strategy necessarily involves attributing responsibility to the other, or when the interests of both are so opposed that counsel cannot represent them loyally and simultaneously.

By contrast, the fact that one pleads guilty and the other does not — without the first defendant's position being used as evidence against the second — does not cross that threshold. A lawyer may, in those circumstances, accompany one defendant through the guilty-plea procedure and simultaneously maintain an active opposition strategy for the other, provided that the exercise of each one's defence does not compromise the other's.

The requirement of independent incriminating evidence

One of the most significant aspects of the judgment is the express confirmation that a conviction of the non-pleading co-defendant requires independent incriminating evidence, untainted by the other's guilty plea. This is consistent with the settled case law on circumstantial evidence and on the evidential limits of a co-defendant's statements.

The LECrim and the Supreme Court's case law have long established that the statements of a co-defendant are not, by themselves, sufficient incriminating evidence to displace the other's presumption of innocence: they may amount to an indication, but require corroboration. A guilty plea has, in this respect, even more limited evidential weight: it is an admission of the pleading defendant's own acts, not testimony about the other defendant's acts.

Practical implications for the defence

The ruling provides clear guidance for those undertaking the representation of several defendants in the same proceedings. Before accepting joint representation, the procedural positions of all the defendants should be analysed for compatibility. If in the course of proceedings one decides to plead guilty and the other does not, counsel must assess whether that split creates a real conflict — assessed in the light of the Supreme Court's criterion — or whether joint representation can be maintained.

The right time to raise the conflict, if one is detected, is as soon as it becomes apparent, not at the cassation stage. A late complaint about a conflict of interest runs into the doctrine of estoppel and the requirement that procedural irregularities be raised at the earliest possible opportunity. Acting in time is an essential part of technically sound criminal defence.

Connection with the right of defence and the presumption of innocence

The judgment of 13 May 2026 sits within a broader line of case law reinforcing procedural safeguards in cases with multiple defendants. The right of defence under Article 24.2 of the Spanish Constitution and the presumption of innocence are individual guarantees: each defendant holds them independently and separately from the position adopted by co-defendants.

For that reason, one co-defendant's guilty plea cannot operate as a kind of implicit acknowledgement of the facts attributed to the dissenting defendant. Criminal proceedings involve multiple defendants, but the guarantees are individual. The ruling restates this with clarity and, in doing so, provides the technical defence with a solid argument against any attempt to use a co-defendant's guilty plea as evidence or an indication against the defendant who maintains their innocence.