In the initial phase, about 100 to 150 detectives were assigned to the case. At the
crime scene, the stream was drained to search for traces. Tracking dogs, metal detectors and probes were used. Unfortunately, this elaborate action brought no results.
The police carried out investigations in Tristan’s surroundings, in Frankfurt’s suburbs, and throughout Germany searching for conspicuous patients of psychiatric institutions or former prison inmates, for war criminals from the former Yugoslavia, and in the French Foreign Legion as well as in other European countries, North America, and Asia.
Correlations with other solved murders were examined without success. Among others, any associations with the cases of the “Cannibal of Rotenburg”, Johanna Bohnacker or Tobias Dreher were eliminated. In order to compare murder cases with a similar patterns of injuries worldwide, the police have worked together with experts from the FBI in Virginia, USA, and with investigators from Europol, among others. To date,
no case with an injury pattern resembling Tristan’s is known anywhere in the world.