to swear that
Oh, podia jurar que vi alguma coisa.
Oh, I could have sworn I saw something.
— A Princesa Prometida (1987)
Eu podia jurar que tinha algo dentro dessa caixa.
I could have sworn there was something inside this box.
Ela me fez jurar que não diria nada.
She made me swear I wouldn't say anything.
— A Vingança de Manon (1986)
Eu poderia jurar que algo se mexeu.
I could swear something moved.
Eles me fizeram jurar que não diria nada.
They made me swear I wouldn't say anything.