I'm listening to "Weekend America" on NPR or PRI or whatever organization produces it. They're talking about forgiveness, and in particular the recently convicted Edgar Ray Killen. They interviewed a pastor from the church which was burned in part to lure the activists to Philadelphia, Mississippi. The pastor, Rev. William Young, talked about the importance of forgiveness, and the fact that Killen's crime was not unforgiveable.
I'm not a trained philosopher or ethicist, so I guess my opinion doesn't count for much in this regard. However, I believe that the only injuries a person has the right or ability to forgive are injuries against himself. Nobody has the right to forgive on someone else's behalf.
In the case of a killing, whether intentional or not, the family and friends of the deceased have suffered injury as well as the deceased. Their pain can be forgiven. The injury to the deceased cannot, however, be forgiven, because the deceased has lost the facility to forgive. Just as he has been deprived of his right to live, he has also been deprived of his right to forgive that deprivation.