With 6% of Europe's freshwater resources, Switzerland is often considered the ‘water tower of Europe’. There are 57’600 farms and 750 wastewater treatment plants (WWTP) in the country. When manure or raw wastewater enters aquatic environment, accidently or intentionally, such pollution can provoke major health risks, contaminating drinkable water sources, or ecological disasters with the death of biota. Among the detected water pollutions, the sources of 25% remain unknown. On one side, it is difficult for environmental law enforcement to initially classify a water pollution (e.g. manure vs WWTP dysfunction), because there is no quick method routinely used on the field. This often hinders following investigation to identify toxic chemicals in the water or potential geographical source in order to target adequate sampling. This works aims at comparing actual practice with potential portable detectors in order to define a forensic approach in water pollution cases investigated by the police.