Good question!
The Catechism says this, and I highlight in bold the part about detraction:
2477 Respect for the reputation of persons forbids every attitude and word likely to cause them unjust injury. He becomes guilty:
–of rash judgment who, even tacitly, assumes as true, without sufficient foundation, the moral fault of a neighbor;
–of detraction who, without objectively valid reason, discloses another’s faults and failings to persons who did not know them;
–of calumny who, by remarks contrary to the truth, harms the reputation of others and gives occasion for false judgments concerning them.
If we are talking about history, and there are lessons we can learn from the faults and failings of others, there may be an “objectively valid reason” to disclose them. To decide this, I think you would have to examine the nature of the person’s faults, the possible harm it may do to his reputation, and the possible benefit to the rest of mankind.
A related question is whether consent can be presumed. If the person had had the chance to consider it prior to his death, would he have agreed to make his faults and failings known? If the benefit to society and to future generations is significant, it is quite possible that someone might set aside his pride and allow the world to know of his mistakes, as if to say “Oh mother, tell your children not to do what I have done.”
johnnyt3000, what kind of faults and failings did you have in mind?