Ermittlung vs Ermittlungen

Question

I've come across the sentence

Die Polizei führt Ermittlungen zu diesem Fall durch.

Are the police really conducting multiple investigations, or is the idiomatic use of Ermittlung usually just in the plural? I've looked at Linguee, and the only sample sentence uses the plural (but the English provided is also "investigations").

The sample usages of Ermittlung on PONS are almost all in plural, too, even if the parallel English is singular.

For what it's worth, the quote above came from a dictionary that provides the transition as "conduct an investigation" (not plural).

Answer 1

"Etwas ermitteln" is to determine a fact by investigating, calculating or other means.

Examples for this basic use of "ermitteln":

Die Staatsanwaltschaft hat für Hinweise aus der Bevölkerung, die zur Ermittlung des Täters führen, eine Belohnung ausgesetzt. (meaning "that lead to identifying the perpetrator")

Sind zwei Seiten eines rechtwinkligen Dreiecks bekannt, kann man die dritte Seite mit den Satz des Phythagoras ermitteln. (meaning: calculate)

Die tägliche Ermittlung der Infektionszahlen war 2020 für die Gesundheitsämter eine Herausforderung. (meaning: compilation, determination)

So if you take into account that, in the original sense, many things must be "ermittelt" to solve a crime case, it's no wonder that "Ermittlungen" is most often in plural in that context.

Uses in singular often refer to something either simple, with a single clear goal, or something more specific that is part of broader "Ermittlungen". For example, in the crime series "Tatort", when the police detective receives a call on their duty cell phone from their SO about of some important personal matter (which will inevitably happen in "Tatort"), the Kommissarin or Kommissar will invariably answer the phone with the line:

Ich kann jetzt nicht reden, ich bin mitten in einer Ermittlung!

Answer 2

From DWDS corpora search I conclude, that you are free to choose in German, whether to use singular or plural.

The reason behind this, is that Ermittlung may represent the whole process of collecting all relevant information as well as any single research step.

Answer 3

The singular version would be this:

Die Polizei führt eine Ermittlung zu diesem Fall durch.

You can translate is as

Police is conducting an investigation on this case.

But also as

Police is conducting one investigation on this case.

This is because the German word »ein« and all its inflections can be interpreted as an indefinite article ("a" or "an") but also as a numeral ("one"). And the unusual usage of the singular form in this statement strongly tends to be interpreted as a numeral.

So, when you use the singular form, you explicitly state, that police is willing to perform only one single investigation and then they will stop any further investigation. So, maybe police want to find out who owns the car in which the robbers fled from the bank, but thats all they do. They are not willing to find out who shot the bank employee, they are not willing to find out who gave them the hint that this bank would be easy to rob and so on.