Der Zeuge sagt aus, dass der Täter das Opfer verfolgt hat.

Because the verb is aussagen, which is a separable verb.

• Infinitive: aussagen
• In a normal main clause, it splits: Der Zeuge sagt aus.

This is very common in German:

• ankommen → Er kommt an.
• aufstehen → Sie steht auf.

So sagt aus is not two unrelated words; it is the verb aussagen split into two parts.

Here aussagen means something like to testify or to give a statement, especially in a legal or police context.

So:

• sagen = to say
• aussagen = to testify / make a statement

That is why Der Zeuge sagt aus sounds more natural than just Der Zeuge sagt in this context. A Zeuge is a witness, so aussagen fits the courtroom/police meaning.

Because dass introduces a subordinate clause, and in German subordinate clauses the finite verb goes to the end.

Compare:

• Main clause: Der Täter hat das Opfer verfolgt.
• After dass: ..., dass der Täter das Opfer verfolgt hat.

So after dass, German changes the usual word order and sends the conjugated verb to the end of the clause.

Because the clause uses the perfect tense and is also a subordinate clause.

The perfect tense is built with:

• auxiliary verb: haben or sein
• past participle: here verfolgt

In a subordinate clause with dass, the finite auxiliary goes to the end:

• Main clause: Der Täter hat das Opfer verfolgt.
• Subordinate clause: ..., dass der Täter das Opfer verfolgt hat.

So hat is last because it is the conjugated verb of the subordinate clause.

In a normal main clause, you usually get:

• Der Täter hat das Opfer verfolgt.

But after dass, the finite verb moves to the end:

• ..., dass der Täter das Opfer verfolgt hat.

So the change is caused by subordinate-clause word order, not by the tense itself.

Both are possible tenses, but they are different.

• verfolgte = simple past / preterite
• verfolgt hat = present perfect

In spoken German, the perfect tense is often more common for many verbs, so verfolgt hat sounds very natural.

You could also say:

• ..., dass der Täter das Opfer verfolgte.

That is grammatical, but it may sound more written or narrative in some contexts.

You know it from the cases and the verb pattern.

In der Täter das Opfer verfolgt hat:

• der Täter is nominative → the subject
• das Opfer is accusative → the direct object

Also, verfolgen normally takes an accusative object: you follow/chase someone.

In this sentence, the forms help too:

• der Täter = nominative masculine singular
• das Opfer = nominative or accusative neuter singular, but here it is the object by function and meaning

So the structure is:

• the perpetrator = the one doing the action
• the victim = the one receiving the action

Yes. These articles show grammatical gender and case.

Dictionary forms are:

• der Zeuge = witness
• der Täter = perpetrator/offender
• das Opfer = victim

In this sentence:

• Der Zeuge is nominative, because it is the subject of sagt aus
• der Täter is nominative inside the dass clause, because it is the subject there
• das Opfer is accusative, because it is the direct object of verfolgen

So the articles are doing important grammar work, not just translating the.

Opfer is grammatically neuter, so the dictionary form is das Opfer, no matter the real-life sex of the person.

So German can say:

• das Opfer war ein Mann
• das Opfer war eine Frau

This is normal. Grammatical gender and biological sex do not always match.

Yes, but the meaning changes slightly.

• Der Zeuge sagt, dass ... = The witness says that ...
• Der Zeuge sagt aus, dass ... = The witness testifies/states officially that ...

The version with aussagen sounds more formal and legal, which matches Zeuge very well.

Because in German, subordinate clauses introduced by words like dass, weil, wenn, and ob are normally separated by a comma.

So:

• Der Zeuge sagt aus, dass ...

This comma is required in standard German writing.

Yes. German allows that.

You could say:

• Dass der Täter das Opfer verfolgt hat, sagt der Zeuge aus.

That is grammatically correct, but it is less neutral and more marked in style. The original version is the more natural everyday order.

When the subordinate clause comes first, the main clause still follows the normal verb-second rule:

• Dass ..., sagt der Zeuge aus.

The sentence has two parts:

1. Main clause: Der Zeuge sagt aus
2. Subordinate clause: dass der Täter das Opfer verfolgt hat

The main clause can stand alone:

• Der Zeuge sagt aus.

But the dass clause depends on it and cannot normally stand alone in the same way:

• dass der Täter das Opfer verfolgt hat = that the perpetrator followed the victim

So dass links the second clause to the first and changes its word order.