How Forensic Chemists are Solving Brazil's Cash Safe Crime Wave
In the dead of night, a thunderous blast shatters the silence of a Brazilian street. An automated teller machine lies in ruins, its contents emptied by unseen criminals. While the perpetrators flee with their loot, they leave behind something crucial: an invisible chemical fingerprint that tells exactly how they committed the crime. This isn't just a story of criminal audacity—it's a tale of scientific detection where forensic chemists work as modern-day alchemists, transforming microscopic residue into compelling evidence.
Brazil has become the unfortunate laboratory for studying ATM explosives, with hundreds of attacks reported annually. Between 2014 and 2020, Brazil's Federal Police documented 93 real cases of ATM and cash safe explosions 3 .
This scientific arms race pits researchers against criminals in a high-stakes battle where chemical analysis has become the key to unlocking the patterns and profiles of a nationwide crime wave.
When explosives detonate, they don't vanish without a trace. Even the most powerful blasts leave behind chemical signatures that can tell a detailed story about what happened. Different classes of explosives break down into characteristic combinations of ions—atoms or molecules with an electrical charge—that serve as their chemical fingerprints.
The workhorse technology for reading these chemical fingerprints is ion chromatography, a sophisticated analytical technique that separates and identifies different ions in a complex mixture. In a recent methodological breakthrough, scientists developed approaches to simultaneously analyze 8 different cations and 18 different anions from a single sample 1 .
Before analyzing explosive residues, scientists face a fundamental problem: the very tools used to collect evidence can contaminate it. In a crucial experiment that changed forensic protocols, researchers made a simple but revolutionary discovery—commercially available evidence collection swabs contained significant levels of various ions that could be mistaken for explosive residues 1 .
The research team implemented a straightforward solution with profound implications: they pre-washed all collection swabs with water. The results were dramatic—this simple washing process "largely removed" the interfering ions, substantially improving the accuracy of forensic analysis 1 .
Purpose: Remove contaminating ions present in swab material
Finding: Higher recovery rates and reduced interference
Purpose: Transfer residue to analysis medium
Finding: Water-moistened swabs improve recovery
Purpose: Preserve chemical integrity
Finding: Critical for maintaining detectable ion levels
Purpose: Identify and quantify ions present
Finding: 8 cations and 18 anions can be simultaneously detected
When applied to real ATM explosion scenes in Brazil, this method proved remarkably effective. The analysis successfully identified key ionic signatures: NO3− and NH4+ in emulsion-based explosives, and ClO4− and K+ in black powder substitutes 1 . These chemical fingerprints allowed investigators to differentiate between explosive types with scientific certainty.
Brazil's experience with ATM explosions provides a disturbing case study in how criminal techniques evolve and spread. The comprehensive analysis of attacks between 2014-2020 revealed clear patterns in the types of explosives favored by criminals 3 .
The predominance of chlorate and perchlorate-based explosives (53% of cases) points strongly to diversion from Brazil's extensive mining industry 3 .
Emulsion explosives (22%) suggest theft from legitimate commercial explosive supplies used in construction and mining operations 3 .
Brazil's criminal innovation isn't limited to explosives. The country has also been the stage for remarkably creative ATM attacks, including one where a thief replaced a machine's security camera with a USB keyboard and proceeded to hack the ATM's computer system, demonstrating the diverse technological capabilities of these criminal networks 6 .
Separates and identifies ionic compounds to detect and quantify anion and cation profiles in residues.
Collect evidence from blast sites while reducing contamination and improving recovery rates 1 .
Preserve evidence integrity by maintaining chemical stability of samples before analysis 1 .
Measures ion concentration in samples and works with ion chromatography to identify and quantify ions.
Beyond the equipment, successful residue analysis requires meticulous attention to procedure. The stability of chemical evidence is affected by numerous factors, from temperature to exposure to light and air. Forensic teams must work against the clock, knowing that some ionic compounds begin degrading almost immediately after collection 1 .
The simultaneous presence of potassium and perchlorate ions strongly suggests a black powder substitute commonly used in improvised explosive devices.
The scientific analysis of ATM explosions extends far beyond solving individual crimes. Each analyzed incident adds to a growing database that helps identify larger patterns in criminal activity, including the diversion of explosives from legitimate industries. The chemical profile of an explosive can sometimes be traced back to specific commercial products or manufacturing batches, potentially leading investigators to the suppliers of these materials 3 .
The global nature of this crime problem is evident in patterns observed elsewhere. In the Netherlands, groups of thieves dubbed "plofkrakers" have developed similar expertise in attacking ATMs with explosives 4 .
Future ATM security lies in systems like Intelligent Banknote Neutralization Systems that stain cash with indelible ink during attacks and enhanced fascia protection 5 .
Chemical tagging of explosives makes them easier to trace back to their sources, creating a deterrent against diversion from legitimate industries.
What began as a local crime problem in Brazil has evolved into a sophisticated forensic science that combines chemistry, materials science, criminal profiling, and security engineering. The silent work of forensic chemists analyzing residue samples in laboratories worldwide represents our best hope for staying one step ahead of those who would use explosives to bypass security. In the enduring battle between criminals and science, it is the meticulous analysis of the slightest chemical traces that often makes the critical difference.
References will be added here manually.