Premeditation in Pink

Lethal Teen Jealousy and the Psychology of the Ana Luiza Poisoning

May 30, 2025, started like any other Friday for 17-year-old Ana Luiza de Oliveira Neves. By 6 PM, she was home in Itapecerica da Serra, a municipality in the state of São Paulo, Brazil. Her sister handed her a pretty package that had arrived earlier, delivered by one of the motorcycle couriers who weave through São Paulo's notorious traffic. Inside was a small cake.

17-year-old Ana

The handwritten note immediately caught Ana's attention. "A treat for the most beautiful girl I've ever seen," a secret admirer had written. A small red heart decorated the message, along with colorful stickers. The note continued: "for the sweetest girl with the best personality that I know." No signature. No name. Just compliments from a mysterious gift giver.

Ana did what any teenager would do—she texted a friend. The messages she sent would later become evidence. "I don't know if it was a friend of mine," Ana said in one. "I wanted to know if it was someone that I want to thank...?" She was curious but not worried. Then came the comment that would prove tragically prophetic: "If I die from poisoning, you'll already know."

She was joking. Sort of. But she ate the cake anyway.

The Murder Weapon

Within an hour, Ana became deathly ill. Vomiting came first, then persistent diarrhea. The teenager who had been fine that morning was now fighting for her life. And no one knew what was wrong.

Ana’s father, Silvio Ferreira das Neves, came home at 1:30 AM. He was terrified by the condition his daughter was in. He immediately drove her to the hospital, where the overnight staff made a swift diagnosis: food poisoning. It was a reasonable diagnosis that would kill her. They gave her antinausea medication, hooked her up to IV fluids, and watched. She got better, and the hospital discharged her later that morning.

But arsenic doesn't give up that easily. By 4 PM, Ana collapsed in her bathroom. This time, during the race back to the hospital, her heart stopped. The emergency team observed cyanosis, the blue discoloration of her lips and fingernails that signals oxygen deprivation. They tried to bring her back. They failed. Ana Luiza de Oliveira Neves died on June 1st, 2025, roughly 36 hours after eating a cake sent by someone who claimed to admire her.

the (as-yet) unnamed suspect

The investigation started when Ana's sister mentioned the strange delivery to their father. Police tracked the motorcycle courier, who led them to the customer who'd hired him. That customer turned out to be a 17-year-old girl who knew Ana well, so well that she'd spent Friday night at the Neves’ house.

Think about this for a moment. This teenager (Brazilian laws prevent the suspect from being publicly named) watched Ana get sick. She witnessed a desperate father rush his daughter to the hospital. She was there Saturday when the family thought Ana was recovering. She was present on Sunday when Ana collapsed. She watched it all unfold, knowing she had caused it. According to Chief Inspector Vitor Santos de Jesus, she "didn't show any reaction at all."

A Chilling Confession

The suspect initially denied everything. But after hours of questioning, she admitted to buying a small cake from a bakery near her home. She'd ordered arsenic trioxide online on May 14th, more than two weeks before she sent Ana the poisoned gift. She mixed the poison into the cake, wrote the flattering note, and paid for the delivery.

Her motive? Jealousy. The specific details of what triggered this jealousy—a boy, social status, or something else—are unclear. What makes her confession particularly disturbing is that Ana wasn't her only target.

A few days before poisoning Ana, this same teenager had sent a poisoned cake to another girl. That victim received a similar note with her toxic gift. She got sick but survived. The suspect later told police she'd targeted this first girl because two of her ex-boyfriends had left her for the victim. Then she moved on to Ana.

The suspect insisted she never meant to kill anyone. She claimed she only wanted to make them vomit, to make them suffer "bad symptoms." She expressed shock at Ana's death and mentioned having mental health problems. She said she was sorry. The suspect was transferred to a young offender institution.

On June 3rd, as she sat in custody, Ana's family and friends gathered to bury a girl who had trusted too easily. Silvio Ferreira das Neves remembered his daughter as "a quiet girl with just a few friends. An innocent girl." Then he added something that captures the real tragedy: "Maybe that's why she ate that cake, without seeing any danger or cruelty in people."

The Psychology of Poisoning

Teenage girls poisoning their rivals is rare, so rare that researchers struggle to find enough cases to study patterns. This scarcity makes Ana's death challenging for those trying to understand and predict this kind of violence among teen girls.

Most adolescent girls who get aggressive stick to familiar territory: nasty rumors, social media harassment, maybe some hair-pulling in the school bathroom. Physical violence happens, but it's usually spontaneous; someone says something, tempers boil over, and fists fly. The girl who plots two poisonings? She's operating in entirely different psychological territory.

Consider what poisoning requires. You can't poison someone on a whim. You need a plan. You need to acquire the poison (in this case, ordering arsenic online). You need a delivery method (such as buying a cake). You need to ensure the victim consumes it (writing a flattering note). Then you need to wait. It requires patience, planning, and emotional distance. The Ana Luiza case demonstrates a sustained intent that lasted over two weeks. That's not a momentary lapse in judgment; that's a commitment to causing harm.

Poisoning also lets the attacker avoid the messy reality of violence. No blood. No screaming. No need to overpower anyone physically. It's the coward's weapon, but also the thinker's weapon. The suspect used a delivery service, adding another buffer between herself and her crime. She could send death by motorcycle courier and then show up to watch the aftermath like a concerned friend. Like a puppeteer pulling strings from behind a curtain, she orchestrated suffering while maintaining the facade of innocence.

The fake admirer’s note adds another psychological layer. This wasn't just deception; it was manipulation designed to ensure Ana would eat the cake. The suspect portrayed herself as someone who thought Ana was beautiful, sweet, someone with "the best personality." This ability to write such words while planning murder suggests a troubling capacity to separate emotions from actions.

The contrast between calculated violence and impulsive aggression becomes clear when examining what happened in Marietta, Georgia, in November 2004. Two 13-year-old girls brought a poisoned cornbread cake to East Cobb Middle School. They'd mixed in bleach, glue, clay, Tabasco sauce, and an expired prescription drug. About a dozen students got sick. All recovered.

The Georgia case differs fundamentally: the girls served the cake themselves to whoever would take it. No specific target. No elaborate planning. No fake love notes. When police questioned them, one father said his daughter had been "bored" and "playing around in the kitchen." He insisted there was no "malicious intent," just a prank that went too far.

The Georgia girls showed poor judgment, but their actions align with typical teenage impulsiveness; failing to consider consequences and not understanding that their "joke" could seriously harm others. They used whatever they found around the house. They got caught immediately.

The Brazilian case shows a calculation that the Georgia girls never approached. Ordering arsenic online isn't something you do while bored in the kitchen. Writing a fake admirer note isn't a spur-of-the-moment choice; it’s a deliberate decision. Using a delivery service is a conscious effort to avoid detection.

Other cases of teenage girls killing rivals involve jealousy. Take Diane Zamora, the Naval Academy midshipman who convinced her boyfriend, David Graham, to kill Adrianne Jones in December 1995. Zamora believed Jones was a romantic rival after Graham confessed to having sex with her. They lured Jones into a car where Zamora hit her with a dumbbell and Graham shot her twice.

Or consider Bernadette Protti, who stabbed popular classmate Kirsten Costas to death in June 1984 in Orinda, California. Protti resented Costas's wealth, looks, and social status. She lured Costas out with a fake invitation to a school activity. When Costas tried to flee, Protti attacked with a kitchen knife.

Both cases share jealousy as a motive, similar to the Ana Luiza case. But Zamora and Protti used weapons that required them to be present, to see their victims' fear, to physically overcome another human being. Using a gun or knife means pushing through the immediate, visceral resistance most people feel toward violence. You have to manage your adrenaline, fear, and your victim's attempts to survive.

Poison eliminates that intense confrontation. The violence happens later, somewhere else, to someone who doesn't even know they're under attack. The poisoner can avoid the psychological weight of direct violence while still achieving their goal.

This distinction between poisoning and physical violence might reflect more than individual psychology. It could also point to cultural and contextual differences in how violence manifests. In the United States, where both the Zamora and Protti cases occurred, firearms are more accessible than in many other countries. The American cultural narrative often frames violence in terms of confrontation and dominance. Even among teenage girls committing murder, the most common methods chosen—guns and knives—require a kind of physical assertion.

The elaborate deception, the use of a traditionally "feminine" delivery method (a sweet cake), and the calculated distance maintained throughout the crime might reflect how violence gets expressed when the perpetrator lacks both the physical means and cultural script for direct confrontation. The sophistication required for poisoning—the planning, the deception, the emotional control—might also appeal to someone who sees themselves as intellectually superior to their victims.

Poison, Jealousy, and Teenage Girls

Poison is often framed in popular literature as being more associated with female perpetrators due to the indirect and premeditated nature of the act. However, empirical data do not consistently support a strong gendered pattern. In adolescent homicides, poisoning is exceedingly uncommon regardless of gender. According to the FBI's Supplementary Homicide Reports, between 2000 and 2020, juvenile female offenders represented roughly 10-12% of all juvenile homicide arrests, and among those, the vast majority used firearms or sharp instruments; poisoning accounted for less than 1% of all methods used by female juveniles. What stands out in Ana's case is not her gender, but the calculated nature of her planning, her concealment of intent, and her apparent emotional detachment from the suffering she caused.

In 1945, mythical detective Sherlock Holmes said, Poison is a woman’s weapon,” and we have yet to live this down. Despite its historical roots, it’s not true. There are more male poisoners than female ones. When we look at actual homicide data, males use poison too, particularly in domestic homicides and cases involving vulnerable victims like the elderly or disabled. The perception persists partly because famous historical poisoning cases, like Mary Ann Cotton or Nannie Doss, captured public imagination and reinforced stereotypes. But data tells a different story: when women kill, they're most likely to use the same methods as men—firearms and knives. The Ana Luiza case is exceptional not because a female used poison, but because a teenager showed such calculated planning.

The Ana Luiza case also raises important questions about psychological escalation. The first poisoning was the beginning of what could have become a pattern. Like a shark that's tasted blood, the suspect wasn't deterred by witnessing her first victim's suffering. Instead, she moved quickly to a second target. This rapid succession, just days between poisonings, suggests either an escalation in violence or a sense of empowerment from the first attack. The second poisoning appeared more emotionally detached, more calculated. This progression mirrors what we see in serial offenders: the cooling-off period shrinks, the violence escalates, and the perpetrator becomes increasingly comfortable with their actions.

That she attempted murder not once but twice, each time employing deception and premeditation, elevates this case beyond the rare and into the extraordinary. In most juvenile offenses, failure often results in retreat or remorse. Here, it appeared to strengthen resolve. The suspect's willingness to refine her method and target a second victim despite witnessing the physical effects on the first reveals not only behavioral persistence but an emerging comfort with lethality.

Motivationally, jealousy remains a key driver in adolescent interpersonal aggression, but lethal outcomes are exceedingly rare. Research has found that jealousy played a role in a majority of female-perpetrated homicides involving female victims. More recent findings confirm that intense interpersonal conflict—including romantic rivalry—is one of the most frequent motivations in adolescent homicides by girls. Yet few of these cases involve poisoning, and even fewer show this level of planning.

In terms of identifying risk, the Ana Luiza case exemplifies the need for updated violence prevention tools that incorporate cyber behaviors, access to hazardous materials, and patterns of social deception. Traditional red flags—such as fighting and overt threats—are absent here. Instead, we see subtler cues: ruminative jealousy, a desire to harm through suffering rather than confrontation, and intellectual planning devoid of empathy. As contemporary threat assessment must evolve to identify these less visible, yet equally dangerous, risk indicators, we see these subtler cues.

The Psychology of Escalation: When Lightning Strikes Twice

The most psychologically compelling aspect here is the rapid progression between victims. Most teenage violence is like a speedboat; loud, visible, everyone sees it coming. This perpetrator was a submarine, moving silently beneath the surface. No fights, no threats, no visible aggression. Just ruminative jealousy, intellectual planning, and emotional detachment. By the time anyone noticed something was wrong, Ana was already dying.

The handwritten note adds another layer, like receiving a hug from someone holding a knife behind their back. This ability to create false intimacy while delivering death suggests sophisticated psychological manipulation despite the perpetrator's young age. Unlike stereotypical "troubled teens," she likely maintained a normal facade. Her calm calculation reveals a chilling comfort with experimenting on human suffering. After all, she knew what was coming. She'd already seen the effects once. She knew the vomiting, the diarrhea, the agony. And she chose to inflict it again, possibly with a stronger dose.

Risk Assessment and the Evolution of Adolescent Violence

The Ana Luiza case forces us to revisit how we evaluate violence risk in teenagers. Standard assessment tools look for obvious red flags: history of fights, animal cruelty, violent threats, substance abuse. A quiet girl who orders arsenic online might fly under every radar.

The internet has fundamentally changed how a determined teenager can secretly obtain poisons. Previous generations could buy arsenic more easily—it was sold at grocery stores and pharmacies as rat poison well into the 20th century. But those purchases were face-to-face, memorable, and traceable. Today's teenagers can research poisons anonymously, order them online with fake information, and have them delivered without any adult ever seeing their face. It's not that poisons are more readily available—they're arguably less so due to regulations—but the anonymity and knowledge about how to use them effectively have increased significantly.

This accessibility requires new ways of thinking about risk. The teenager who spends weeks researching poisons online leaves digital footprints that didn't exist before. The suspect in Ana's case created a trail, including online searches, purchase history, and delivery records. But someone needs to be looking for these signs.

The pattern of escalation also matters. The suspect poisoned two different girls within days, with the second attack proving fatal. This progression from non-lethal to lethal poisoning suggests someone becoming more comfortable with violence, more willing to risk serious consequences. It's a pattern we sometimes see in serial offenders—the time between attacks shrinks, the violence escalates, the perpetrator becomes emboldened. Like an avalanche that starts with a few pebbles and builds to devastating force, her actions gained deadly momentum.

I’m skeptical of the suspect's claim that she only wanted to make her victims sick. This teenager watched her first victim become violently ill from the poisoned cake, ill enough to require medical attention. Yet she proceeded with her second attempt just days later. Whether she increased the arsenic dose for Ana or got "lucky" with a fatal outcome the second time, her actions after witnessing the first poisoning's effects demolish any claim of innocent intent. She knew precisely what arsenic could do to a human body. She'd seen it firsthand. And she did it again.

Our prefrontal cortex, the part responsible for understanding long-term outcomes, isn't fully developed until we are in our mid-twenties. As such, teens can plan complex actions without truly comprehending their permanent effects. But this biological fact doesn't excuse murder. It might explain the disconnect between planning and consequence, but it doesn't diminish culpability.

For those working with teenagers, this case highlights the danger of dismissing jealousy as typical adolescent drama. Most teenage jealousy leads to nothing worse than mean texts or tears. But when combined with other risk factors—social isolation, emotional detachment, and obsessive rumination—jealousy can metastasize into something deadly. Like cancer cells that multiply silently before symptoms appear, dangerous obsessions can grow beneath a normal exterior.

The warning signs in cases like this differ from typical violence indicators. We're not looking for the kid who gets in fights or makes threats. Instead, the red flags might include:

• Obsessive focus on perceived rivals or romantic interests

• Research into harmful substances or methods of causing illness

• Expressions of intense jealousy that seemed disproportionate to the situation

• Social withdrawal combined with rumination about others' relationships

• Previous attempts to manipulate or control social situations through deception

The challenge is that many of these behaviors, taken individually, might seem like typical teenage drama. It's the combination and intensity that signal danger. A teenager researching chemistry might be doing homework. A teenager researching poisons while expressing jealousy about specific individuals presents a different picture entirely. It's like the difference between someone buying a knife for cooking and someone buying a knife while discussing how much they dislike their neighbor.

The sophistication shown in Ana's murder also challenges assumptions about teenage violence being impulsive and poorly planned. This teenager spent two weeks preparing. She researched her method, acquired her materials, and executed her plan while maintaining a normal facade. That's not impulsivity—that's premeditation of a type we usually associate with adult criminals.

Traditional violence prevention focuses on identifying and intervening with obviously troubled youth—the ones getting into fights, making threats, showing clear aggression. The challenge lies in identifying someone whose violence simmers beneath a calm surface, who smiles at their victim while planning their murder.

Ana Luiza de Oliveira Neves was 17 years old. She had friends who cared about her and a father who loved her. She had a trusting nature. After her death, Ana’s father said that his daughter “didn’t see the danger or cruelty in others. “ This speaks to her character, not her judgment. The question isn't why Ana ate the cake (as, unfortunately, several commenters focused on). It’s why another teenager felt entitled to poison her. And in an age where arsenic is just a click away, how can we do better at spotting and stopping those who would exploit others' kindness for deadly purposes?

References

Federal Bureau of Investigation. (2019). Crime in the United States, 2019: Expanded Homicide Data. U.S. Department of Justice. https://ucr.fbi.gov/crime-in-the-u.s/2019/crime-in-the-u.s.-2019/topic-pages/expanded-homicide

Heide, K. M., Roe-Sepowitz, D. E., Solomon, E. P., & Chan, H. C. (2014). Girls arrested for murder: an empirical analysis of 32 years of U.S. data by offender age groups. International Journal of Offender Therapy and Comparative Criminology, 58(9), 1053-1073.

Ingraham, C. (2015, May 7). Poison is a woman's weapon. The Washington Post. [Analysis of FBI Supplementary Homicide Reports, 1999-2012]

Lewis, D. O., Moy, E., Jackson, L. D., Aaronson, R., Restifo, N., Serra, S., & Simos, A. (1985). Biopsychosocial characteristics of children who later murder: a prospective study. American Journal of Psychiatry, 142(10), 1161-1167.

As always, thanks for reading this edition of The Mind Detective. Please pass along to your true-crime-following friends. And, if there’s a case you’d like me to cover, please reach out.