Breakdown of Бухгалтер клянётся в своей невиновности.
бухгалтер
accountant
свой
one's own
в
of (in accusations, confessions, oaths)
клясться
to swear
Questions & Answers about Бухгалтер клянётся в своей невиновности.
Why does the verb клянётся take в plus the prepositional case here?
Verbs expressing strong conviction, assurance, or insistence, like клясться (to swear) and убеждать (to convince), require в + prepositional case to introduce the concept being insisted upon. While English uses 'swears to' or 'swears by', Russian structures this as swearing 'in' a fact, hence в своей невиновности.
Why is своей used here instead of его for 'his'?
Because the accountant is swearing to his own innocence. Whenever a possessive pronoun refers back to the subject of the sentence, Russian requires the reflexive possessive свой. It is declined as своей to match the feminine prepositional noun невиновности. Using его would mean he is swearing that some other man is innocent.
Why does невиновности end in -и if it is in the prepositional case?
The dictionary form is невиновность (innocence), which is a feminine noun ending in a soft sign (-ь). Nouns in this specific feminine declension group always take an -и ending in the prepositional case, rather than the standard -е ending you see on most other nouns.
Does the -ся ending on клянётся mean he is doing something to himself?