Die Staatsanwaltschaft und die Verteidigung prüfen das Beweismittel.

Because the subject is actually two nouns joined by und:

• die Staatsanwaltschaft
• die Verteidigung

Together, they form a plural subject, even though each noun is singular by itself. In German, that means the verb must be in the 3rd person plural form:

• sie prüft = she/it examines
• sie prüfen = they examine

So:

• Die Staatsanwaltschaft und die Verteidigung prüfen ... = correct
• Die Staatsanwaltschaft und die Verteidigung prüft ... = incorrect

In this sentence:

• Die Staatsanwaltschaft und die Verteidigung = the subject
• das Beweismittel = the direct object

You can tell this in a few ways:

1. Verb agreement
   The verb prüfen is plural, which matches the two-part subject die Staatsanwaltschaft und die Verteidigung.

2. Meaning of the verb
   prüfen usually takes a direct object: you examine something.
   Here, that something is das Beweismittel.

3. Case
   The verb prüfen takes the accusative case, and das Beweismittel is in the accusative.
   In this case, das looks the same in nominative and accusative because the noun is neuter, so the form alone does not fully reveal the case. The sentence structure and verb help you identify it.

Because both nouns are feminine singular nouns:

• die Staatsanwaltschaft
• die Verteidigung

In the nominative singular, feminine nouns use die.

So here:

• die Staatsanwaltschaft = the prosecution / public prosecutor’s office
• die Verteidigung = the defense

Even though both use die, they are still singular nouns individually.

Because Beweismittel is a neuter noun, so its singular article is das:

• das Beweismittel = the piece of evidence / the evidence item

In this sentence it is singular, so you use das, not plural die.

A useful note: the plural is also die Beweismittel.
So:

• singular: das Beweismittel
• plural: die Beweismittel

Here is the case breakdown:

• die Staatsanwaltschaft → nominative
• die Verteidigung → nominative
• das Beweismittel → accusative

Why?

• The subject of the sentence goes in the nominative
• The direct object of prüfen goes in the accusative

So the structure is:

[Subject in nominative] + [verb] + [direct object in accusative]

Because in German, all nouns are capitalized, not just proper names.

So in this sentence, these words are capitalized because they are nouns:

• Staatsanwaltschaft
• Verteidigung
• Beweismittel

This is a general German spelling rule, and it helps learners spot nouns more easily.

Yes, both are compound nouns, which are very common in German.

Staatsanwaltschaft

This is made from:

• Staat = state
• Anwalt = lawyer
• -schaft = a noun-forming ending

Historically and structurally, it refers to the public prosecutor’s office or prosecution service.

Beweismittel

This is made from:

• Beweis = proof / evidence
• Mittel = means / instrument

So Beweismittel literally means something like means of proof, which corresponds to evidence or piece of evidence.

German often combines words into one long noun where English uses separate words.

Yes, German word order is flexible, but the finite verb still has to stay in the second position in a normal main clause.

The original sentence is:

• Die Staatsanwaltschaft und die Verteidigung prüfen das Beweismittel.

You could also say:

• Das Beweismittel prüfen die Staatsanwaltschaft und die Verteidigung.

This puts more focus on das Beweismittel.

What does not change is the verb placement rule:

• one element first
• the finite verb second

So German does not work like English in terms of fixed subject-verb-object order, but it is still highly structured.

You usually do repeat the article here because these are two separate nouns, each with its own article:

• die Staatsanwaltschaft und die Verteidigung

Leaving out the second die would sound unnatural in standard German in this sentence.

Repeating the article makes it clear that you are talking about two distinct groups or roles.

The infinitive is prüfen, meaning to examine, to check, or to review.

Here is the present tense conjugation:

• ich prüfe
• du prüfst
• er/sie/es prüft
• wir prüfen
• ihr prüft
• sie/Sie prüfen

In the sentence, the subject is effectively they, so you use:

• prüfen

Grammatically, it is a singular feminine noun, but semantically it often refers to an institution rather than one individual person.

Depending on context, die Staatsanwaltschaft can mean:

• the public prosecutor’s office
• the prosecution
• sometimes, by extension, the prosecuting side

So even though it may refer to a group or office in real life, German treats it as a singular noun. That is why, by itself, it would take a singular verb:

• Die Staatsanwaltschaft prüft das Beweismittel.

But once you add und die Verteidigung, the whole subject becomes plural:

• Die Staatsanwaltschaft und die Verteidigung prüfen das Beweismittel.

It can mean either, depending on context.

Verteidigung can refer to:

• the act of defense
• the legal defense
• the defense team / defense side in a trial

In this sentence, because it appears with die Staatsanwaltschaft and both are doing something in a legal context, it most naturally means the defense as one of the parties in the case.

German often uses abstract-looking nouns like this to refer to institutions or sides in a legal process.

Yes. This is a very good sentence to read as:

• Subject: Die Staatsanwaltschaft und die Verteidigung
• Verb: prüfen
• Object: das Beweismittel

So it follows a straightforward pattern:

The prosecution and the defense examine the evidence.

That said, German can move parts of the sentence around more than English can, as long as the verb-position rules are respected. But the version you were given is a very standard, clear main clause.