The case known as “The Poisoner of Guaymallén” took place in Guaymallén, in the province of Mendoza, and involved Karen Leilen Oviedo, who was convicted of poisoning her partner, Ángel Rolando Aquino, and his young son, Elián Aquino.

What happened

In January 2021, Rolando Aquino was hospitalized with severe symptoms, including abdominal pain, confusion, and organ failure. Doctors quickly suspected poisoning rather than natural illness. He died two days later.

Police began investigating Karen Oviedo, his partner, after inconsistencies appeared in her statements. She claimed he had taken “healing drops,” but investigators found no such product. Testimony from a housekeeper and forensic evidence raised serious suspicion.

The key mistake: Google searches and online purchases

Digital forensic analysis of Oviedo’s phone and computer revealed incriminating evidence, including searches such as:

• “Which is the deadliest poison?”

• “How to kill with poison”

• “How to delete search history”

Investigators also confirmed she had purchased ethylene glycol (antifreeze) online. This toxic chemical is colorless, odorless, and has a sweet taste, making it difficult to detect when mixed in drinks.

These searches and purchases directly linked her to the poisoning and showed premeditation.

Connection to the earlier death of a child

During the investigation, authorities reopened the 2019 death of Rolando’s 9-year-old son, Elián. He had suddenly died after similar symptoms. Medical experts concluded that his symptoms were also consistent with ethylene glycol poisoning.

Evidence showed that Oviedo had purchased antifreeze shortly before his death as well.

Trial and sentence

In December 2022, after reviewing digital evidence, medical findings, and witness testimony, a jury found Karen Oviedo guilty of both murders.

She was sentenced to life imprisonment for:

• The aggravated homicide of Rolando Aquino

• The aggravated homicide of Elián Aquino

Why “Google gave her away”

The phrase refers to how her internet activity became critical evidence. Her search history, combined with purchase records and timing, demonstrated planning and intent. This digital trail helped prosecutors prove the murders beyond reasonable doubt.

The case became one of Argentina’s most disturbing criminal investigations and highlighted how digital evidence can play a decisive role in solving crimes.