Colombian Poison Mystery Grows Darker as Serial Killer Fears Spread

What began as the alleged poisoning of two Colombian schoolgirls has now expanded into a web marked by recurring thallium, intimate grudges, and multiple women falling ill in similar circumstances. This development forces prosecutors to reconsider whether they are investigating a single crime or, instead, a disturbing pattern.

The Box That Changed Everything

On April 3, 2025, according to Colombia’s attorney general’s office, contaminated raspberries were sent by courier to a residence in Bogotá and consumed by minors. Two girls died, and two other young people survived after being exposed, turning what first looked like a grotesque act of revenge into one of Colombia’s most unnerving recent poisoning cases. Prosecutors later sought the extradition of Zulma Guzmán Castro on aggravated homicide and attempted homicide charges. She denies the allegations.

The first version of the story already had the shape of a true crime. A private grudge. A gift delivery. A poison slipped into something sweet. British reporting and Colombian case material say investigators believe the alleged attack was tied to Guzmán Castro’s past relationship with Juan de Bedout, the father of one of the girls. But what makes the case feel less like a single revenge plot and more like a possible serial poisoning file is what investigators say they found when they looked backward.

Toxicologists have long considered thallium a notorious homicide tool. A recent review notes it’s called “the poisoner’s poison,” while U.S. guidance cites human poisonings typically involve hair loss, numbness, limb pain, and digestive issues. Here, several women involved developed symptoms so confusing that poison was initially mistaken for illness.

The Women Before the Girls

The narrative then reaches into the past, beginning with Alicia Graham Sardi, Juan de Bedout’s wife, who died in August 2021 after a cancer relapse. What once seemed to fit the tragic logic of disease has since been reopened by toxicology findings. El Colombiano reported that investigators now believe Alicia suffered two separate thallium poisonings before her death—despite the original medical conclusion listing cancer—and that later blood studies on Juan de Bedout and one of his sons also showed traces of thallium. Another report in the same outlet said Alicia’s body contained between eighty and ninety micrograms of the metal, that she initially improved after treatment aimed at clearing it, and later deteriorated again before dying in Europe.

That is where the case acquires its most chilling texture. In ordinary murder stories, violence announces itself. Here, it may be hidden inside symptoms. British and Colombian reporting has described Alicia as suffering hair loss and severe leg pain before her death, details that now land differently because they fit the symptom pattern toxicologists associate with thallium exposure. In hindsight, that kind of overlap can make a case feel haunted. Not because the clues were supernatural, but because they were biological and still failed, at first, to say murder clearly enough.

The second woman now shadowing the file is a relative identified in Colombian reporting as Elvira Restrepo, described locally as Guzmán Castro’s sister-in-law. Attorney General Luz Adriana Camargo said investigators have evidence of at least one other similar poisoning involving a relative and the same method, which is why the case has started to be discussed in Colombia, not just as a double homicide but as a possible serial murder investigation. El Tiempo’s reporting, visible in search results, says investigators are examining another box of chocolates allegedly sent to that relative in a separate episode roughly a year before the girls died.

That detail is what true crime readers immediately recognize as a pattern. Not simply poison, but repeated poison. Not simply one target, but an orbit of women around the same emotional geography. Not simply a method, but a method dressed up as care. Media reports in Colombia and Britain say Restrepo became seriously ill after receiving chocolates and required treatment first in Bogotá and then in the United States. Even with the usual caution that must surround an unresolved case, the sequence is hard to ignore: sweets, sickness, thallium, family proximity, and investigators returning again to the same name.

Across Borders, the Pattern Follows

As the investigation grew, Guzmán Castro surfaced in London, expanding the case beyond Bogotá. Colombia’s Fiscalía says it first issued an Interpol red notice and then formalized an extradition request after learning she was in the United Kingdom. The agency’s 2025 to 2026 report says the extradition request was formally presented by Colombia’s embassy on December 19, 2025, and that she was captured and placed before Westminster Magistrates’ Court on January 6, 2026.

British reporting adds the eerie final image that has helped seal this case into the public imagination. The Standard reported that Guzmán Castro was pulled from the River Thames near Battersea Bridge in December, was later held under the Mental Health Act, and then arrested by the National Extradition Unit once doctors cleared her for discharge. She refused to consent to extradition at an initial hearing. That does not prove guilt. What it does do is extend the mystery across jurisdictions, turning a Colombian poisoning file into a transatlantic test of evidence, procedure, and time.

Camargo’s intervention was what most sharply changed the tone of the case. She said investigators do not see the deaths of the girls as an isolated episode and that the evidence points toward repetition of the same criminal pattern. That is prosecutor language, technical and careful. But its emotional meaning is stark. Serial cases are not defined by spectacle. They are defined by recurrence. And recurrence is exactly what prosecutors say they are now testing here.

The central mystery has thus evolved. It is no longer just a question of who sent one deadly package, but whether the poisoned raspberries reveal a broader pattern finally coming into view. If Colombian prosecutors can connect earlier incidents involving women to the same method, the case will shift from looking like a single act of obsession to reading as something colder, slower, and far more methodical. In true crime, that is the point where dread deepens: the monster is no longer a burst of rage, but patience.

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