Learn Swedish: Svaranden kan överklaga domen. - The defendant can appeal the verdict.

It comes from the present participle of svara (to answer). When present participles are used as nouns to describe a person doing an action, they become common gender words. The base noun is en svarande (a defendant or respondent), and adding the definite suffix makes it svaranden (the defendant).

Is överklaga a separable verb here?

No, it is a fixed compound verb meaning "to appeal". It is built from över (over) and klaga (to complain). You cannot split this into "klaga över" to mean "appeal" in a legal context, because "klaga över" just means to complain about something in everyday speech.

Is the root word of domen pronounced the same as the spoken pronoun dom (they/them)?

No. The noun en dom (a verdict or judgment) is pronounced with a short, closed "o" sound (similar to the vowel in the English word "room" or "book"). The pronoun dom is pronounced with a short "å" sound.

How is domen related to the Swedish verb for "to judge"?

The noun en dom is the root of the verb att döma (to judge or to sentence). Notice the vowel change from o in the noun to ö in the verb, which is a common historical pattern in Swedish when deriving verbs from nouns.