Updates to our Terms of Use

We are updating our Terms of Use. Please carefully review the updated Terms before proceeding to our website.

Saturday, June 15, 2024 | Back issues
Courthouse News Service Courthouse News Service

Mandatory pretrial detention ruling revives questions over power of Mexico Supreme Court

A case arguing that the preventative measure violates human rights as defined in international treaties to which Mexico is signatory has Supreme Court justices quarreling over whether or not their appellate power extends to the country’s Constitution.

MEXICO CITY (CN) — A ruling expected from Mexico's Supreme Court on Tuesday has the potential to change the fates of tens of thousands of people held in the country's prisons without convictions.

But the decision on the constitutionality of mandatory pretrial detention will also determine the extent of the Supreme Court’s regulatory jurisdiction.

The court began debate Monday on suits brought by the National Human Rights Commission and several senators claiming that mandatory pretrial detention violates Mexico’s Constitution.

Chief Justice Arturo Zaldívar opened the debate by calling the initiative “one of the most important proposals that has been presented in the history of this tribunal.”

Justice Luis María Aguilar brought the case before the court, saying: “When limits on personal liberty such as mandatory pretrial detention are established, it must be done with great care, as the limits or restrictions that are established cannot be absolute, but rather the opposite. They must be exceptional and only applicable under extraordinary and grave circumstances.”

While the suits aim to eliminate mandatory pretrial detention for a number of crimes, ranging from homicide to organized crime to auto theft, the case has broader legal implications due to the cautionary measure’s enshrinement in the Mexican Constitution.

Although she called the issue a “justified social complaint,” Justice Yasmín Esquivel Mossa said Monday that she planned to vote against unconstitutionality, stating that she does not “share the idea that this Supreme Court has the powers to nullify a regulation” of the Constitution.

Three other justices also expressed their intentions to vote against unconstitutionality before the court adjourned Monday. 

A supermajority of eight of the court’s 11 justices is required to deem a law or regulation unconstitutional, so it appears that the initiative will be rejected, no matter where the six remaining justices fall on the issue.

Currently, the jury is out on the Supreme Court's ability to nullify an article of the Constitution. The debate resides in whether or not the international treaties dealing with human rights that Mexico has signed trump its own Constitution.

Justice Loretta Ortiz Ahlf, one of the four who expressed her intention to vote against unconstitutionality Monday, agreed that mandatory pretrial detention violates the United Nations International Covenant on Civil and Political Rights and the American Convention on Human Rights. She placed the onus of complying with the treaties on the Congress, stating: “I hope it does.”

The entrance sign to the Santa Martha Acatitla women's prison. Officially named a "Reintegration Center," many inmates say they have spent years in pre-trial detention. (Cody Copeland/Courthouse News)

Even court precedent waffles on the issue. 

A 2011 case that put international treaties on the same level as the Constitution stated that in the event that harmonization between the two is impossible, judges should apply “the criterion that turns out to be more favorable for the protection of people’s human rights.”

However, the ruling also states that “when in the Constitution there is an express restriction of the exercise of [human rights], it must be what the constitutional text establishes.”

“It’s contradictory, I know, but that’s how the Mexican Supreme Court is,” said Sergio López Ayllón, a research professor in the law department at the Mexico City-based government think tank CIDE.

“The Mexican Supreme Court does have broad powers to interpret the Constitution,” said López. “It has the final say.”

However, that 2011 ruling put both Article 19 of the Constitution and the international prohibition of what that article stipulates on the same legal standing, and now the court, legal experts and politicians disagree on which should prevail.

“Given that both are considered to be of constitutional rank, which one should be applied?” said López. “Here is where the court is divided.”


As of June, over 90,000 people were incarcerated without convictions in Mexico, according to Intersecta, a feminist human rights organization that filed an amicus brief in the case in August.

“The problem with mandatory pretrial detention is that it does not comply with standards for issuing a cautionary measure, and it ends up acting as an advance sentence,” said Haydeé Gómez, a legal analyst at Intersecta. 

Intersecta analyzed the most recent prison census data from Mexico’s national statistics agency Inegi and found that over 40% of people in the country’s prisons in 2021 had not been convicted of a crime. 

Most of those (24.8% of men and 29.7% of women) had been in custody for less than three months, while some (12.6% of men and 14.2% of women) had been in pretrial detention for more than the legal limit of two years. 

Some inmates in the Santa Martha women's prison in Mexico City told Chief Justice Arturo Zaldívar in May that they had been in mandatory pretrial detention for as long as 15 years.

“It’s part of the narrative of punitive populism, that if we continue to expand this authority and we keep incarcerating people, it will in some way reduce criminal behavior, but the evidence shows us that this is completely false,” said Gómez. “Moreover, it makes the historically vulnerable even more so.”

Mexican President Andrés Manuel López Obrador stands during the commemoration of his second anniversary in office, at the National Palace in Mexico City, on Tuesday, December 1, 2020. (AP Photo / Marco Ugarte )

Intersecta’s analysis shows that mandatory pretrial detention predominantly affects the poor and un- and undereducated. Two thirds of people in mandatory pretrial detention in 2021 did not have beyond a secondary education. Another 21.8% had not gone beyond high school. Nearly 60% earned the equivalent of $375 a month, and just under a quarter did not even earn Mexico’s minimum wage for that year, less than $150 a month. 

While the elimination of mandatory pretrial detention has a determined advocate in the Supreme Court — Zaldívar pledged to take action after that unprecedented visit to the Santa Martha women’s prison — it has found a staunch opponent in the executive branch. 

President Andrés Manuel López Obrador vehemently opposes the elimination of the measure, despite its negative effects on the very sector of society he claims to champion, and asserts that it will only generate more corruption in Mexico’s judiciary.

But as Justice Aguilar and amicus curiae Intersecta pointed out, the suit does not aim to eliminate all forms of pretrial detention, only the mandatory one referred to as “oficiosa” in the Constitution. 

Justified pretrial detention, by which a judge determines whether or not the accused should be remanded based on the specifics of the individual case, would remain in force. This measure is enforced if the court decides that the defendant may fail to appear in court, is a danger to witnesses or victims, or could otherwise obstruct the administration of justice. 

“I insist that pretrial detention will continue, but in a justified and motivated manner,” said Aguilar. 

Gómez, the Intersecta lawyer, decried political narratives claiming that droves of criminals will be freed if mandatory pretrial detention is eliminated as fear mongering not rooted in reality.

“The Mexican government, specifically the executive branch, has spread the fake news that all the criminals — both those presumed innocent and those proven guilty — are going to be let out of prison,” she said. “This is not true. The point is that they would review all the cases.”

She said that forcing the country’s judges to examine pretrial detention on a case-by-case basis would incentivize attorney generals and police to conduct investigations, something direly lacking in Mexico’s criminal justice system.

“Mandatory pretrial detention doesn’t only affect the accused, it also affects the victims, because it does not involve the issuance of justice,” she said. “It only imprisons people who are presumed innocent until the contrary is proven.”

Follow @copycopeland
Categories / Appeals, Courts, Criminal, International

Subscribe to Closing Arguments

Sign up for new weekly newsletter Closing Arguments to get the latest about ongoing trials, major litigation and hot cases and rulings in courthouses around the U.S. and the world.