無罪だと

that someone is innocent

→ 無罪だ
phrase Rare #36,680
that someone is innocent Used before verbs such as 信じる (to believe), 言う (to say), and 抗議する (to protest) to express the content of a statement or belief. 無罪 means “not guilty” or “innocent.”
JA: 彼は無罪だと主張している。
EN: He claims that he is innocent.

彼女は威厳をもって自分は無罪だと抗議した

She protested her innocence with dignity.

私は、彼がその事件について無罪だと信じています

I believe he is innocent of the incident.

この国では無罪だと牢屋どういうこと

What do you mean, “In this country, being found innocent gets you thrown in jail”?

— ほんとうのピノッキオ (2019)