GEN1439 Even if the speaker’s intentions are entirely good, he must take care [to tell the truth]. Chofetz Chaim, Hilchos Lashon Hara 10-2. … Any statements he makes must be strictly true, and contain no element of exaggeration.   Furthermore, if the subject is alleged to have violated the Torah, the speaker must be certain that his understanding of the relevant halachos is accurate and that he is applying them correctly to the case at hand.   Often, the right or wrong status of an action depends on many intricate details, and an individual who makes a quick judgment based on superficial or secondhand knowledge of the facts is likely to err. Therefore, it is important both to investigate all the circumstances thoroughly and to consult with a qualified rav regarding any halachic considerations. In Parshas Vayeishev Yosef misjudged his brothers’ actions and concluded incorrectly that they were guilty of certain sins. He was guilty of lashon hara for relating this information to this father Bereishis 37:2. EHRMAN 197-8