百口莫辩（百口莫辯）　

◎ 百口莫辩 bǎikǒu-mòbiàn

[unable to give a convincingexplanation for self-defense] 百:言其多;莫:不;辩:辩解。即使长很多嘴也辩解不清

自知中计而百口莫辩