R. Mark Dratch of JSafe published an article titled "Couldn’t Be! Do Alleged Perpetrators of Abuse Deserve the Benefit of the Doubt?" (link - PDF) which discusses the need to maintain a balance between judging someone favorably and being cautious. Here's an excerpt:
How do we resolve the tension between the requirement to judge favorably on the one hand, and the need for caution and suspicion on the other? One answer is to make a distinction between those we know who generally behave appropriately and strangers whose motives and dispositions are unknown to us. The former require our sympathetic assessment, the latter do not. Others suggest that one should be wary and suspicious of others, but he must treat them respectfully as if they were innocent.Read more here (PDF).
Consider the Mishnah, Yoma 18b, which relates how the priestly elders charged the High Priest prior to his officiating in the Temple’s Holy of Holies on Yom Kippur. To ensure that he would follow the rituals according to the rabbinic, Pharisaic requirements, and not in accord with the interpretations of the Saduccees...
The Talmud explains that “he turned aside and wept” because they suspected him of being a Sadducee, and they turned aside and wept for having suspected him and not judging him favorably. Rambam, in his commentary on the Mishnah dealing with the exhortation of the elders of the High Priest before Yom Kippur states that positive presumptions are suspended with regard to strangers when there is a hekhreh gadol, a critical need to do so...
Furthermore, the obligation to judge others favorably, according to the Mishnah, applies to all people, including the accuser. If we are to give others the benefit of the doubt, we must do so for the accuser as well. We are not to assume automatically that the allegations are false, nor are we to assume automatically that the accusations are true. We must treat all parties with deference, as if all were innocent of wrong doing, but we must investigate carefully and thoroughly, and in a timely manner. Of course, as we shall see, we must also act with great prudence, assuring that those who make the accusations as well as other innocents do not come to harm either by further abuse or by retaliation of the accused.
In addition, we cannot let our favorable judgment cause us to ignore possible violations of Jewish law. The Torah obligates us to rebuke those who have sinned as well as to protect the safety and welfare of the community. Automatically deciding another’s innocence prevents these obligations from being fulfilled. And this obligation of rebuke applies even when the one accused of doing wrong is one’s parent or teacher...