The Vaud cantonal police had international assistance. Interpol was involved from early in the investigation, providing coordination across borders given that the case had attracted attention across Europe and North America, and that the perpetrators — as would eventually be established — were Eastern European immigrants living in Switzerland rather than Swiss nationals.
The photograph Wardas sent of the coffin was a crucial development. It eliminated doubt about whether the caller had what he claimed, and it provided physical evidence of the coffin’s condition and location. Contemporary reporting does not describe what the photograph showed in detail beyond establishing that it depicted the coffin in a field setting. The Swiss National Museum’s 2023 blog account notes that the photograph showed the coffin “beside a hole in the cornfield,” which gave investigators a setting that could eventually be matched to a geographic area.
Tracing the photograph’s origin required analysis of the image itself — what vegetation was visible, what the soil looked like, what landmarks if any appeared at the edges. This kind of investigation is slow and not always productive. The SwissInfo account says the photo was “later traced to Noville,” without specifying what evidence made that connection possible or when during the investigation the link was established.
The telephone surveillance operation — the monitoring of 200 payphones — was the most resource-intensive phase. The Vaud cantonal police later said publicly that it was the largest operation in their history. Deploying that many officers requires sustained organizational commitment and, importantly, a degree of confidence that the target will use one of the boxes being watched. The fact that police committed to covering the Lausanne area specifically suggests they had established through earlier tracing that Wardas’s calls were coming from payphones in and near Lausanne, even if they could not identify which specific box he would use.