According to national media reports, Zaw Lin described in court how he was assaulted by police investigating the killings, which took place on a Thai island in September last year.
He also claims that a translator assaulted him.
Zaw Lin has previously claimed that he was stripped, blindfolded and had plastic bags placed over his head during questioning.
The prosecution claims that Zaw Lin and his co-accused Wei Phyo, both aged 22, freely confessed to raping and murdering Miss Witheridge (23) and murdering Mr Miller (24).
However, the pair claim they only confessed because they were tortured.
The trial continues.
Source: Sky News
