Here the word "We" refers only to the men they persuaded to lie. The word "they" refers back to the people from the synagogue of the freemen in [Acts 6:9](../06/09.md). (See: [[rc://en/ta/man/translate/figs-exclusive]])
This phrase means they could not prove false what he said. Alternate translation: "could not argue against" (See: [[rc://en/ta/man/translate/figs-idiom]])