Akademik

не пойман не вор
НЕ ПОЙМАН - He BOP
[saying] a person should not be considered guilty of a wrongdoing if he is not caught at the scene of the crime (said when there is no irrefutable evidence of s.o.'s guilt; sometimes said with regret when s.o.'s obvious guilt cannot be proven): innocent until proven guilty; a thief isn't a thief unless you catch him in the act; a thief isn't a thief till hefc caught (in the act).
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     ♦ "А откуда вам известно про его штуки?" - "Говорили в институте..." - "Чего ж вы ему тогда холку не намылили?" - "Не пойман - не вор" (Семёнов 1). "How do you come to know so much about his tricks?" "They were talked about at the Institute. ..." "Why didn't you settle his hash at that time?" "You're not a thief till you're caught" (1a).

Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. . 2004.