From the river Thames to Colombia: extradition and forensic keys in the thallium poisoning case

Diaz Reus | A Technical-Investigative Analysis of Criminal Responsibility, Mental Health, and International Judicial Cooperation

The case of the poisoning of minors in Colombia through the ingestion of raspberries contaminated with thallium has quickly transcended the domestic criminal sphere to become a matter of international concern. The gravity of the events, the nature of the toxic agent used, and the subsequent departure from the country of the main suspect have necessitated a much broader legal and forensic analysis, one that integrates criminal law, forensic psychiatry, and international judicial cooperation.

In December 2025, the thallium poisoning case culminated in the location of the main suspect, Zulma Guzmán Castro, who was rescued from the River Thames in London after months on the run. The crime occurred in April 2025 in Bogotá, where two minors died after ingesting strawberries (raspberries) contaminated with this toxic metal, allegedly sent by Guzmán as personal retaliation against the father of one of the victims; the woman is currently in British custody awaiting an extradition process requested by the Attorney General’s Office (Fiscalía General de la Nación) to face charges of aggravated homicide.

1. The criminal act: intentional poisoning with Thallium
From a forensic perspective, thallium is considered one of the most dangerous heavy metals due to its high toxicity, the difficulty in its initial detection, and its capacity to cause severe systemic damage. The Colombian investigation determined that its inclusion in food intended for children was not accidental, but rather the result of deliberate acts clearly aimed at causing harm.

This element is crucial for structuring the charges of aggravated homicide and attempted homicide, given the presence of factors such as the victims’ special defenselessness, the use of poisonous substances, and the plurality of victims.

2. The international dimension of the case
Given the risk of flight, Colombian authorities activated international judicial cooperation mechanisms, requesting the issuance of an Interpol Red Notice. This instrument does not imply a pre-trial conviction, but it does allow for the location and provisional arrest of the wanted person for extradition purposes.

The departure from the country and the subsequent placement in the United Kingdom shifted the legal debate to an international criminal law scenario, where principles of sovereignty, protection of human rights and obligations of cooperation between States converge.

3. The River Thames Incident and Its Procedural Impact
The rescue of the suspect from the River Thames in London introduced a critical procedural element: the alleged serious impairment of her mental health. In accordance with British protocols, emergency services prioritized medical attention and psychiatric evaluation, postponing any immediate legal proceedings.

From an investigative perspective, this type of episode makes it necessary to differentiate between an authentic clinical crisis and behavior that is potentially instrumentalized for procedural purposes, especially in contexts of extradition for extremely serious crimes.

4. Mental Health, Legal Capacity, and Extradition in the United Kingdom
The British system, through the National Health Service (NHS), has robust protocols for independent psychiatric assessment. These assessments aim to establish the person’s actual clinical condition, suicide risk, and, especially, their capacity to understand and participate in a legal process (fitness to plead).

The eventual legal incapacity does not extinguish the criminal action, but may lead to temporary postponements until a minimum level of stability is reached. In extradition matters, the courts only suspend the proceedings if a real and immediate risk to life or the existence of inhuman or degrading treatment is demonstrated, standards that are evaluated with particular rigor in cases of homicide of minors.

5. Forensic and Strategic Implications
From the perspective of criminal investigation and legal strategy, the allegation of psychiatric impairment can lead to two clearly distinct scenarios. If it is a malingering or exaggeration, the consequence is usually a loss of credibility before the courts and a strengthening of the requesting state’s position. If, on the other hand, the impairment is clinically real, the proceedings are temporarily suspended, medical stabilization is ordered, and the legal process is subsequently resumed.

In neither scenario does mental impairment constitute a mechanism for impunity. Criminal responsibility remains subject to the technical, objective, and independent verification of medical and forensic evidence.

About the author:

Carlos F. Salazar is a criminal investigator and forensic auditor. He began his professional career as a homicide investigator and later joined specialized anti-corruption units within the Colombian Attorney General’s Office.

In private practice, he directs CFS Strategic Investigations, a firm with a presence in Colombia, Panama, and the United States, specializing in corporate fraud investigations, corruption, economic crimes, complex homicides, and asset recovery. He is part of the global DRT Alliance network, led from Florida by Diaz Reus International Law Firm.

His work focuses on designing investigative strategies and techniques aimed at challenging and refuting prosecution hypotheses through the rigorous analysis of physical and digital evidence, the identification of methodological flaws, and the objective pursuit of truth in highly complex criminal proceedings.