"Joseph, being seventeen years old, was feeding the flock with his brethren, being still a lad even with the sons of Bilhah, and with the sons of Zilpah, his father's wives; and Joseph brought evil report of them unto their father." Genesis 37:2 (JPS).
From contemporary views on halacha, it seems that it would be bad to report ("speak lashon hara") about anyone - even if the issue is a true wrongdoing. Nevertheless, the Torah seems to suggest that we are sometimes required to present evidence of bad behavior to a judge.
Was Joseph speaking lashon hara or was he simply giving a factual report to his father, the judge, about something gone bad?