The Torah does not accept circumstantial evidence as proof of a person’s guilt. Thus, when one suspects an individual of improper behavior, he may not decide that his suspicions are correct based on the person’s reactions to accusations or other strange behavior that strongly points to his guilt.
Nevertheless if, in addition to the circumstantial evidence, such suspicions are subsequently supported by someone else’s claim to have actually witnessed the person engaging in such behavior, one does have the right to believe that his suspicions are correct.
However, to whatever degree possible, the listener is still obliged to judge the perpetrator favorably; he must seek to understand his motives and should not be swift to condemn him.
Moreover, one may not pass on the information without fulfilling the preconditions for relating negative information for a constructive purpose.