Mandatory Pretrial Detention in the Face of the New Judicial Landscape in Mexico

Prof Dr James Cavallaro (left)

James is the Executive Director of the University Network for Human Rights, and a visiting professor at Columbia Law School, Nova Law School in Lisbon, Portugal, and Yale Jackson School of Global Affairs. He served as Commissioner, Rapporteur on the Rights of Persons Deprived of Liberty, Rapporteur for Mexico, and as President of the Inter-American Commission on Human Rights (IACHR).

Dr Sofía Galván Puente (right) Sofía is a Senior Clinical Advisor and Supervisor at the University Network for Human Rights. For a decade, she worked as a specialist in the Executive Secretariat of the IACHR. One of her roles was as the lead lawyer for the Rapporteurship on the Rights of Persons Deprived of Liberty.

Introduction

With the stated objective of guaranteeing peace and security, the recent constitutional reform on pretrial detention — in effect as of January 1, 2025 — expanded the list of offenses for which mandatory pretrial detention must be applied. In addition to failing to fulfill the purpose for which it was promoted, this reform clearly contradicts international standards on the matter.

Mere accusation of conduct included on the list of mandatory pretrial offenses–even without solid evidence–is sufficient for a person to be imprisoned for months or even years before trial. Granting this power to the authorities expands their range of action, both lawful and unlawful, and thus increases the possibility of it being used arbitrarily.

It is no coincidence that modern societies have developed strict measures and practices to guarantee the rule of and protect individuals’ rights against the State’s devastating power to deprive someone of their liberty based solely on an accusation. In the international sphere, these safeguards are enshrined in human rights law and are fully applicable in Mexico through the implementation of the principle of conventionality control (“control de convencionalidad”). Based on this principle, all authorities must adopt practices or make decisions in light of the obligations contained in the international human rights treaties ratified by Mexico.

In the context of the recent reform of the Judiciary, the arbitrary application of mandatory pretrial detention is likely to intensify. In the face of a compromised judicial independence and the prioritization of political considerations over merit in the selection processes of judges, a clear risk emerges: that the relevant authorities may ignore or fail to fulfill their obligation to apply the principle of conventionality control. As a result, greater challenges will arise in ensuring that the restriction of an accused person's liberty is based solely on the legitimate purposes that justify the application of the most severe measure — and not merely on public outcry for peace and security.

Definition and Consequences of the Use of Mandatory Pretrial Detention

Pretrial detention consists of the provisional incarceration of a person during the investigation phase to determine their criminal responsibility. Such detention before trial is considered the most severe precautionary measure that can be imposed on a defendant because it results in imprisonment without a conviction. Specifically, mandatory pretrial detention applies “when certain crimes are alleged without the authorities having the ability to determine the purpose, necessity or proportionality of the precautionary measure in each case.”

Mandatory pretrial detention poses various challenges in terms of human rights. In particular: (i) it contradicts international standards in the field of international human rights law, as well as the obligations Mexico has assumed through the ratification of various international instruments; (ii) it falls far short of achieving its intended goal of addressing legitimate public security concerns; (iii) it directly harms and violates the rights of persons in situations of vulnerability, such as those living in poverty and women; and (iv) it contributes to the increase in prison overcrowding, which in turn results in additional human rights violations.

With the increase in the prison population and the resulting overcrowding in correctional facilities, conditions arise that endanger the life and integrity of incarcerated persons. According to the Inter-American Commission on Human Rights (“the Commission” or “IACHR”), overcrowding — among other effects — hinders access to basic services, facilitates the spread of disease, and limits external contact. Additionally, it fosters corruption and creates serious challenges in prison management, leading to a lack of effective control over detention centers. Furthermore, mandatory pretrial detention is a practice characteristic of authoritarian regimes.

Mandatory Pretrial Detention in Mexico

Various statements issued by international human rights bodies have expressed grave concerns about the proposed constitutional reforms on mandatory pretrial detention. In this regard, the United Nations Working Group on Arbitrary Detention, the Office of the United Nations High Commissioner for Human Rights in Mexico (“OHCHR”), and the IACHR have all expressed their opposition. Additionally, in two recent cases against Mexico — Tzompaxtle Tecpile et al and García Rodríguez and another  — in relation to the mandatory pretrial detention, the Inter-American Court of Human Rights (“IACHR Court”) ordered the State “to adapt its legal system, including its constitutional provisions, so that it is compatible with the American Convention”. Both cases are currently in the compliance monitoring stage.

Despite this, then-President Andres Manuel López Obrador (“AMLO”) promoted the use of mandatory pretrial detention as part of a security policy that prioritized incarceration to address public security problems in Mexico. According to the Inter-American Court, such policies are driven by “vindicative discourses and highly emotional messages” responding to “opportunistic” reasons. In fact, there is international consensus on the lack of empirical evidence supporting the purported correlation between these policies and a reduction in crime. In contrast, there is evidence — for example — that the application of pretrial detention increases recidivism rates. Further, the use of this mandatory makes public resource allocation less efficient and stigmatizes communities.

In April 2019, during the first year of AMLO’s term, a constitutional reform that promoted greater use of mandatory pretrial detention was enacted. In particular, that reform established this measure for 16 offenses. Near the end of his term, on February 5, 2024, AMLO presented Executive Initiative No. 6457.5. This proposal aimed to amend, again, Article 19 of the Constitution to expand the list of crimes subject to the application of this mandatory pretrial detention.

On January 1, 2025, under the administration of Mexico’s first female president, Claudia Sheinbaum, the proposed amendment to Article 19 of the Constitution came into effect. As a result, the current catalogue of offenses warranting mandatory pretrial detention includes activities related to the production and distribution of fentanyl, its derivatives and precursors, as well as smuggling and falsifying tax receipts. At the same time, the current constitutional text, in its second paragraph, prohibits the analogous or extensive interpretation of the rule, establishing:

For the interpretation and application of the provisions set forth in this paragraph, State bodies must adhere to their literal meaning, and any analogous or extensive interpretation that seeks to disregard, suspend, modify, or nullify its terms or validity, whether in whole or in part, is prohibited.

The Recent Judicial Reform

The judicial reform in Mexico was a proposal presented in February 2024, alongside the one related to mandatory pretrial detention, by former President López Obrador. On September 15 of the same year, the constitutional reform was published in the Official Gazette of the Federation (Diario Oficial de la Federación). Among the measures it introduced was the popular election of all judicial authorities, from the lowest levels to the ministers of the Supreme Court of Justice. The first elections were held on June 1, 2025. This September, the new judges — including the ministers of the Supreme Court of the Nation — will begin their terms. The election of the other half of the judges will take place in 2027.

One of the main concerns of international human rights bodies (such as the Special Rapporteur on the Independence of Judges and Lawyers, the OHCHR, and the IACHR) is that with popular elections as the method for selecting judicial authorities, political considerations will override the “objective merits” of the candidates. Additionally, these bodies have expressed concern about the early termination of existing judicial mandates, the creation of the Judicial Discipline Tribunal as an institution that may compromise judicial independence, and the establishment of measures to preserve the anonymity of justice operators.

The Use of Pretrial Detention Within the Framework of the Current Judicial Reform

The recent reform to the Judiciary will almost certainly lead to an increase in the use of mandatory pretrial detention. This is mainly because the reform limits judicial independence and creates a clear risk that the principle of conventionality control will not be properly applied.

According to the Inter-American  Court, one of the main human rights impacts caused by mandatory pretrial detention is the limitation of the judicial authority’s role, resulting in acts effectively exempt from any real control. Since pretrial is engaged by the constitutional provision alone, judges lack discretion to decide on its application. If this issue is placed within the context of judicial reform—which, as noted by the Special Rapporteur on the Independence of Judges and Lawyers and the IACHR, compromises judicial independence—we face a scenario in which  it will not be possible to protect one of the most basic guarantees of due process and the rule of law.

Moreover, non-compliance with what is known as conventionality control  (a mechanism incorporated into the constitutional text since the 2011 constitutional reform on human rights) is expected. Conventionality control is the tool that allows authorities, based on the pro persona principle, to grant the highest protection in human rights matters. This is done by verifying the conformity of national laws and practices with the American Convention on Human Rights, the jurisprudence of the Inter-American Court, and other inter-American treaties to which the State is a party.

In light of the recent judicial reform, there is an evident risk: that judicial authorities will ignore or fail to fulfill their obligation to apply conventionality control. This is because the overriding of objective criteria in the selection of judges may result in a lack of capacity or aptitude to appreciate and apply international human rights law when it grants the highest protection. In this context, judges would be unable to prevent the application of a norm that—although constitutional—is unconventional and contrary to the pro persona principle.

There is no doubt that the latest reform on pretrial detention, especially in the current context, raises serious concerns within the criminal justice and human rights framework. The proper exercise of conventionality control is more necessary than ever in the face of two unanticipated reforms that are reshaping Mexico’s justice system: (i) a judicial reform and the resulting challenges to justice it entails, and (ii) the reform on mandatory pretrial detention that aggravates arbitrary incarceration by promoting greater use of mandatory pretrial detention.

Based on all of the above, we believe that the use of conventionality control—which applies to all authorities, not just judicial ones—constitutes one of the few opportunities to guarantee due process and prevent arbitrary application of a penalty imposed in advance on those who have not been convicted. We urge those able to do so to advocate for its robust application.

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