In April 2018, eight police officers in Pilar, Argentina, were dismissed after their explanation for a huge hole in their evidence store fell apart. Around 540 kilograms of seized cannabis, more than half a tonne, had vanished from a police warehouse. The officers' explanation? Mice had eaten it. Forensic experts and a federal judge did not believe a word of it.
What happened in the Pilar police warehouse
Pilar is a town in Buenos Aires province, north-west of the Argentine capital. Its police kept impounded drugs in a storage facility, and according to reports at the time the records showed roughly 6,000 kilograms of cannabis there. When an inspection was carried out, only about 5,460 kilograms could be found. The missing 540 kilograms had, on paper, simply disappeared.
According to press accounts, the discrepancy came to light after a change of leadership. Javier Specia, the former police commissioner responsible for the depot, had reportedly left his post in 2017 without properly signing off the inventory of seized cannabis. His successor, named in reports as Emilio Portero, noticed the shortfall and alerted the authorities, which led to a formal inspection of the warehouse.
When questioned by Judge Adrián González Charvay, Specia told him that mice had raided the store and eaten the drugs. His colleagues gave the same account. In mid-April 2018, all eight officers were dismissed, and they were scheduled to give evidence to the judge in early May.
Why the "mice ate it" excuse did not hold up
Investigators found no sign of a rodent feast. Experts from the University of Buenos Aires, consulted for the case, made two simple points. First, mice "wouldn't mistake the drug for food". Second, if enough mice had eaten that much cannabis, "a lot of corpses would have been found in the warehouse". No such evidence turned up.
A quick calculation shows how far-fetched the claim is. A typical house mouse weighs around 20 to 30 grams and eats only a few grams of food a day. Even if every mouse in the building ate nothing but cannabis, munching through 540 kilograms over the two years the drugs were stored would require hundreds of mice eating constantly, all without leaving droppings, nests or bodies behind. And dried, compressed cannabis bricks are not an obvious food source for rodents, whatever growers say about mice nibbling young plants and seeds in the field.
The story went viral around the world because the excuse sounded like a grown-up take on "the dog ate my homework", as one US radio station put it at the time.
UP there with "the dog ate my homework"! "The mice ate the weed! So help me GOD - the MICE at the weed!" - dan mac #Wow #STONED : Fired cops claim mice ate marijuana that was held as evidence. https://t.co/Ftld592D4X
— 93.9 The River (@939theriver) April 16, 2018
Why missing evidence is a serious problem
It is easy to laugh at this story, but missing evidence is no joke for the justice system. Seized drugs are physical proof in criminal cases. If they disappear, or if their chain of custody cannot be shown, prosecutions can collapse and defendants can walk free, or be wrongly convicted if records are faked to cover the gap.
Missing drugs also raise an obvious question: where did they go? Half a tonne of cannabis has a significant street value, and evidence that leaves a police store can end up back on the illegal market. That is why the court treated the case as a matter of possible corruption rather than a pest-control problem.
Good evidence handling is not complicated in principle: every item logged, sealed and signed for; regular audits; restricted access; and prompt destruction of drugs once a court no longer needs them. The Pilar case, according to the reports, broke down at the very first step, with an inventory left unsigned during a handover.
Not the only time animals have been blamed
Pilar was not a one-off. Police in other countries have also pointed at rodents when seized drugs went missing. In one widely reported case from 2022, police in Mathura, in India's Uttar Pradesh state, reportedly told a court that rats had eaten hundreds of kilograms of cannabis held as evidence. Courts and the public tend to react the same way each time: with disbelief and a demand for proper record-keeping.
Rodents really can damage stored goods, so it is not absurd that a few bags might be nibbled. But there is a large gap between some gnawed packaging and half a tonne vanishing without a trace.
What science says about cannabis and mice
The story prompted a lot of online jokes about stoned mice, and some articles claimed that research shows cannabis is "good for mice". The real science is more mixed.
In 2017, a team led by Andreas Zimmer at the University of Bonn published a study in Nature Medicine showing that a chronic low dose of THC, the main psychoactive compound in cannabis, restored learning and memory performance in old mice aged 12 and 18 months, making their brains look more like those of young animals on several measures. But the same treatment given to young mice, aged 2 months, impaired their performance on learning and memory tasks.
Another 2017 study, in the Journal of Neuroscience, looked at adolescent mice and found that THC changes how certain neurons in the brain's reward system adapt, which the authors suggested could help explain cannabis's rewarding and potentially addictive effects in young people.
In other words, results depend heavily on age and dose, and findings in mice do not automatically apply to humans. Neither study suggests that mice seek out cannabis as food, and neither makes the Pilar officers' story any more believable.
Cannabis law in Argentina
At the time of the scandal, cannabis for personal recreational use was not legal to sell in Argentina, although the country passed a law in 2017 permitting research into, and medical use of, cannabis oil. Courts had also long debated whether possessing small amounts for personal use should be punished. Large seizures like the one in Pilar, however, were firmly in the territory of drug trafficking cases, which is why the missing evidence mattered so much.
Whatever your view on cannabis laws, the lesson of this story is not really about the plant. It is about trust. When police are entrusted with evidence, they need to be able to account for it, and an explanation involving an army of invisible mice is not going to satisfy a judge.
Sources: TimesLIVE: Cops fired after claiming mice ate 540kg of missing marijuana (citing The Guardian and BBC News); Bilkei-Gorzo et al., Nature Medicine (2017); Friend et al., Journal of Neuroscience (2017). Images: The Mystery Vault, Royal Queen Seeds and CTV News; tweet by 93.9 The River.
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