Accuse (someone) behind (someone's) back
Translation of "accuse (someone) behind (someone's) back" into Russian
accuse (someone) behind (someone's) back
обвинить (кого-то) за спиной (кого-то)
It's not fair to accuse her behind her back without proof.
Неправильно обвинять её за спиной без доказательств.