Before dawn on April 24, 2017, the Paraguayan city of Ciudad del Este – an important trading hub between Brazil, Paraguay and Argentina – was besieged by heavily armed criminals. For hours the city was terrorized by gunfire and violence. Streets were blocked and vehicles set on fire. The criminals' target was the main cash-transit company in the region, Prosegur, which has a large central hub in that city. After the robbery, the criminals fled to Brazil, carrying more than 11 million dollars stolen from the company.

At daybreak, all the newspapers reported what had happened. Faced with a crime of enormous proportions, unprecedented in the region, they soon began to call this event the “Robbery of the Century” [1].

This triple border region has a Tripartite Command, which enables police collaboration between the cities of Puerto Iguazu (Argentina), Foz do Iguaçu (Brazil) and Ciudad del Este (Paraguay) [2]. In this context, the Brazilian Federal Police acted from the beginning, conducting the crime scene investigation and forensic analysis.

In the following hours, a house used by the gang as “headquarters” was located in Ciudad del Este. There were dozens of objects with potential for genetic analysis and identification of criminals. In addition, several other crime scenes interconnected with this robbery were located, such as more than ten vehicles stolen during the escape and some shootings sites where bags and backpacks were abandoned.

The forensic work culminated in the collection of 457 traces with potential use for genetic exams. All were sent to the DNA laboratory of the National Institute of Criminalistics, in Brasilia (Federal District). At that time, cases commonly received by the laboratory had an average of 4 to 5 related traces. In this way, the Prosegur case represented the equivalent of 100 ordinary cases, which was a great challenge.

As an urgent and priority investigation, the laboratory team had to dedicate itself fully to this case. The laboratory experts were divided into groups: a group responsible for sampling, analysis of results and writing of reports and a group dedicated for laboratory benchwork, responsible for all workflow from extraction to genotyping. In addition, two experts were dedicated to process reference materials and one expert was responsible for managing the DNA Database. All of this was coordinated by the head of the laboratory, who communicated between the laboratory experts, the investigation team and the Directors.

Many of the traces were analyzed in the first ten days after the materials were received at the laboratory. It helped to keep some of the suspects arrested in prison. At the end of processing all materials, around 580 samples were obtained and analyzed, which generated 47 different genetic profiles, 11 of which with identified sources.

Since 2013 Brazil has an Integrated Network of DNA Databases (RIBPG) that aims to share and compare genetic profiles stored in the DNA Databases of the States, the Federal District and the Federal Police [3]. Nowadays, RIBPG has one national database and twenty-two local databases that are located in the DNA laboratories of the Federal Police, the Federal District and 20 Brazilian states. They all communicate with the National DNA Database, which allows for the exchange of genetic profiles at an interstate and interagency level.

Currently, the Brazilian National DNA Database has more than 150,000 genetic profiles [4], being the largest DNA Database in Latin America. Most of these are genetic profiles of convicted offenders, who have had their DNA collected as permitted by Brazilian criminal law [5].

In view of this existing structure in Brazil, the genetic profiles obtained from the Prosegur case were uploaded to the RIBPG databases. In National and Federal Police DNA Databases, 17 profiles matched with other profiles from 21 unrelated crime scenes, resulting in the identification of 7 more individuals. These matches linked the Prosegur robbery in Paraguay to crimes in six different Brazilian states between 2013 and 2020, committed by a large criminal organization, the First Capital Command (PCC).

Among the individuals already tried and convicted, the penalties applied for participating in this robbery ranged from 24 to 34 years in prison, plus a fine. This was the largest case ever analyzed by a DNA laboratory in Brazil and helped to demonstrate to the country's institutions that the evidence obtained by DNA tests can be essential for the application of justice.

Furthermore, the numbers and results obtained in this study represent a unique situation not directly comparable with other studies, both on controlled samples and on real casework samples. Due to this scenario, which is unprecedented in the scientific literature, the detailed analysis of this case made it possible to carry out an extensive study about the nature of the biological traces collected at real crime scenes and the respective obtainment of interpretable genetic profiles.

Briefly, the following results were observed regarding the categories of samples obtained:

• the 457 pieces of evidence collected can be divided into 45 different types of biological traces and substrates;
• 94% of the samples obtained can be classified into four major biological trace groups: wearer DNA, buccal epithelium/saliva, “touch DNA” and blood;
• Wearer DNA was the most common biological trace, sampled from 271 items of 14 different types, ranging from clothes and shoes to bed linen, bath towels and ballistic vests.

Regarding obtaining interpretable genetic profiles, the following was observed:

• 42.7% of the samples of buccal epithelium/saliva resulted in interpretable genetic profiles (84.8% of the samples amplified), being the type of biological trace with the best results;
• 24.4% of the samples of wearer DNA resulted in interpretable genetic profiles (55.9% of the samples amplified);
• only 6.4% of the samples of “touch DNA” resulted in interpretable genetic profiles (17.8% of the samples amplified);
• considering the total samples obtained, the overall DNA yield was 41.6% and the DNA profiling success rates were 23.9%, respectively. Considering only amplified samples, the profiling success rate was 57.7%;
• About 88.4% of the genetic profiles eligible for comparisons were obtained from wearer DNA (47.8%, proportional to the great number of traces received) or buccal epithelium/saliva samples (40.6%, proportional to the expected large amount of intact DNA in these samples).

On the substrates, the following results were obtained:

• The substrates that most resulted in interpretable profiles were cigarette butts, underwear, towels, balaclavas, pants/shorts and t-shirts;
• Substrates such as soap, hair, toilet paper, license plates, ammunition, ballistic vests, drain lid and miscellaneous packaging did not result in reportable genetic profiles.

Thus, the analysis of the data obtained during the DNA exams of the "Robbery of the Century" helped the scientific and forensic community. Furthermore, such a study is now a guide for forensic experts who work at crime scenes with regard to the main traces that can be collected and that have a greater chance of offering interpretable genetic profiles and, consequently, greater possibilities of identifying criminals.

The investigation of this crime, strongly based on forensic genetic exams, reached international repercussions. In 2020 the “Robbery of the Century” was selected the DNA Hit of the Year, a recognition of the value of DNA database technology to solve and prevent crime [6]. Currently, this case serves as proof of the efficiency of forensic genetics in solving crimes and in combating criminal organizations.

This manuscript summarizes the results presented in the article “The ‘Robbery of the Century’: the biggest Brazilian forensic genetics case”, recently published in Forensic Science International: Reports [7].