He protested his innocence.

他声言自己无罪。

youdao

He always protested his innocence and claimed that the drugs had been planted to incriminate him.

他一直坚称自己是清白的，声称毒品是有人放置要栽赃于他。

《柯林斯英汉双解大词典》

He protested his innocence to no avail.

NPR: NSA Operations Remain Opaque to Investigators

He has always protested his innocence, arguing that eye witness evidence was mistaken.

BBC: William Beck loses armed robbery conviction appeal

He has repeatedly protested his innocence and went on hunger strike in December.

BBC: NEWS | Americas | Argentine denies abuse knowledge