A server seized in Geneva. Evidence that took years to cross borders. More than 155,000 files eventually handed over for analysis in Bern. And, eight years after the original seizure, testimony before a court in Lima.
This is one strand of Operation Lava Jato, the investigations that exposed Odebrecht’s system of secret payments across Latin America and beyond.
The Swiss strand of the investigation involved Stefan Lenz, today a partner at LENLAW in Bern, who supported Peruvian prosecutors, analysed evidence originating from Switzerland and eventually explained that evidence before a Peruvian court.
Stefan Lenz and Óscar Solórzano together with representatives of the Peruvian prosecution service.
By 2016, the Swiss investigation had moved beyond suspicious bank transactions. Swiss investigators had secured electronic data connected with Odebrecht’s Structured Operations Division, the unit used to administer secret payments.
The material included data from MyWebDay, which recorded financial transactions, and Drousys, a protected communication system.
The significance of the discovery went beyond individual documents. MyWebDay and Drousys offered a way of connecting payments with intermediaries, bank accounts and recipients across different jurisdictions.
The discovery solved one problem and created another: the evidence existed, but the prosecutors who needed it were thousands of kilometres away.
That gap between finding evidence and actually being able to use it abroad became one of the defining features of the years that followed.
Building the bridge to Peru
By the end of 2016, Peruvian prosecutors were trying to obtain evidence and trace funds through foreign financial centres. This required more than a conventional criminal investigation. Mutual legal assistance requests had to be prepared, foreign authorities engaged and, where assets could be located, recovery strategies developed.
Peru was not trying to build that bridge alone. Among those helping its prosecutors navigate foreign jurisdictions was Óscar Solórzano, a Peruvian-Swiss lawyer specialising in asset recovery. As head of the Basel Institute on Governance’s activities in Peru, Solórzano accompanied Peruvian prosecutors to Switzerland in December 2016 and worked with the authorities on international cooperation and asset recovery.
By then, Lenz had left the Swiss Federal Prosecutor’s Office and returned to private practice.
In early 2017, he prepared a proposal for the Peruvian authorities centred on the practical questions now confronting them: Who had been involved in the payments? Who were the ultimate recipients? Which intermediaries had been used? And through which bank accounts had the money moved? The proposal also contemplated the recovery and repatriation of assets.
Contacts followed between Lenz, Solórzano and the Peruvian prosecution service. By August 2017, Peru had formally engaged Stefan Lenz and his team as external advisers in the Odebrecht investigation.
Stefan Lenz and Óscar Solórzano with members of the Peruvian prosecution service during the cooperation with Peru.
The value of the arrangement was continuity. Peru did not simply receive documents generated by a foreign investigation; it could draw on people who understood how those documents had been obtained, what they represented and how they fitted into the wider financial picture.
That continuity would become increasingly important, because obtaining the underlying data took years.
From Bern to a courtroom in Lima
Peru sought the original MyWebDay and Drousys material through international legal assistance. Litigation in Switzerland delayed the transmission, illustrating a recurring difficulty in cross-border cases: knowing where the evidence is can be much easier than obtaining it in a form that can actually be used.
It would take almost four years before that bridge finally carried the evidence itself.
Peruvian prosecutor José Domingo Pérez travelled to Bern and handed Lenz two data carriers at the Peruvian Embassy. Together they contained more than 155,000 files from MyWebDay and Drousys. Peru commissioned Lenz to analyse them.
Peruvian Prosecutor José Domingo Pérez with Stefan Lenz at the Peruvian Embassy in Bern
According to IDL-Reporteros’ later review of Lenz’s reports, 19,735 files were identified as relevant to the Peruvian investigations. The analysis was not simply a search for names or payments. The analysis examined how Odebrecht’s secret payment systems worked, how the recovered information fitted together and where the different datasets had come from.
Three years later, that work reached a very different setting.
In April 2024, former Peruvian president Alejandro Toledo was standing trial in Lima in connection with Odebrecht and the Interoceánica highway project. The Peruvian Public Prosecutor’s Office called Stefan Lenz as an expert witness to explain the Swiss seizure, the Odebrecht systems and his subsequent analysis of the data.
Eight years after the evidence had first been secured in Switzerland, knowledge of how it had been obtained and understood had itself become relevant in a Peruvian courtroom.
Solórzano was again part of the wider cooperation effort. By then Head of Latin America at the Basel Institute’s International Centre for Asset Recovery (ICAR), he was in Lima as part of an ICAR delegation together with Lenz and Diana Cordero.
A story that outlived one trial
The Toledo proceedings did not entirely close the chapter. In 2025, a Peruvian court admitted Lenz’s testimony and one of his reports as new evidence in proceedings concerning former Lima mayor Susana Villarán.
Almost a decade after the original Swiss investigation, the same body of evidence was still making its way through the Peruvian justice system. In between lay years of mutual legal assistance, financial analysis, data review and cooperation between people working in different legal systems.
That is often the reality of cross-border economic crime: progress depends less on a single dramatic breakthrough than on keeping hold of the evidence, the relationships and the strategy as a case moves from one jurisdiction to another.
Sources and further reading
Swiss evidence and the Odebrecht systems
The Swiss investigation produced electronic evidence that later became central to the Peruvian proceedings. These sources document Stefan Lenz’s direct involvement with the Swiss evidence, the MyWebDay and Drousys systems and their later analysis for Peru.
Ministerio Público del Perú — 9 April 2024
Equipo Especial Lava Jato toma declaración de testigo experto Stefan Lenz durante juicio oral a Alejandro Toledo
Official account of Stefan Lenz’s role in the Swiss seizure of Odebrecht data and his later testimony as an expert witness before a Peruvian court. The publication links the Swiss investigation directly to the Toledo proceedings in Lima.
Read the original publication
IDL-Reporteros — 21 November 2021
El informe Lenz
Detailed reporting on Lenz’s analysis of MyWebDay and Drousys, including the identification of 19,735 files considered relevant to the Peruvian investigations and the reconstruction of Odebrecht’s secret payment systems.
Read the article
International cooperation and asset recovery
Peru’s investigation depended on cooperation with foreign jurisdictions. These sources document the role of Óscar Solórzano, the Basel Institute on Governance and Stefan Lenz in international legal assistance, financial investigation and asset recovery.
SWI swissinfo — February 2017
Instituto suizo apoya a Perú en gran caso de corrupción
Interview with Óscar Solórzano, who leads the Basel Institute’s work in Peru, on supporting Peruvian prosecutors with international cooperation, mutual legal assistance and the recovery of assets located abroad.
Read the article
IDL-Reporteros — April 2017
El documento que se esfumó
Reports on the proposed work programme prepared through LENLAW for the Peruvian authorities. It included the identification of payment recipients, financial intermediaries, bank accounts and assets inside and outside Peru, as well as measures relating to asset recovery and repatriation.
Read the article
El Comercio — August 2017
Ex fiscal suizo ya asesora oficialmente al Ministerio Público en investigación del caso Odebrecht
Reports on the formal engagement of Stefan Lenz and his team as external advisers to Peru’s Public Prosecutor’s Office in the Odebrecht investigation.
Read the article
Obtaining and analysing the Swiss data
The transfer of evidence from Switzerland to Peru took years. These sources document both the mutual legal assistance process and the subsequent large-scale analysis of electronic evidence.
Convoca — 2020
Odebrecht obstruye en Suiza envío al Perú de base de datos original
Reports on the legal proceedings surrounding Peru’s efforts to obtain the original Odebrecht database from Switzerland and illustrates the difficulties of cross-border evidence gathering in international corruption proceedings.
Read the article
Ministerio Público del Perú — 31 August 2021
Ministerio Público encargó a experto suizo más de 155 mil archivos para analizar datos sobre sobornos Odebrecht
Official confirmation that the Peruvian prosecution service handed more than 155,000 MyWebDay and Drousys files to Stefan Lenz in Bern for analysis. This provides a direct public record of his role in analysing complex electronic evidence for a foreign prosecution authority.
Read the original publication
From investigation to courtroom
The same body of evidence later became relevant in Peruvian criminal proceedings. These sources document the transition from international investigation and evidence analysis to expert testimony in court.
Ministerio Público del Perú — 9 April 2024
Equipo Especial Lava Jato toma declaración de testigo experto Stefan Lenz durante juicio oral a Alejandro Toledo
Official account of Lenz’s expert testimony in the Alejandro Toledo trial, concerning the Swiss seizure, the Odebrecht systems and his subsequent analysis of the data.
Read the original publication
Basel Institute on Governance — 2024/2025
Following the money: how Peru reshaped corruption investigations after Odebrecht
Retrospective on Peru’s work in financial investigations, international cooperation and asset recovery, including the ICAR delegation with Stefan Lenz, Diana Cordero and Óscar Solórzano at the Toledo proceedings.
Read the article
El Comercio — 2025
Nuevas pruebas admitidas en el juicio contra Susana Villarán
Reports that a Peruvian court admitted Lenz’s testimony and one of his reports as new evidence in later proceedings concerning former Lima mayor Susana Villarán.
Read the article