JOEL - I searched all Conference talks and here is what Elder Packer said in 1995:

The Brilliant Morning of Forgiveness: Elder Boyd K. Packer (October 1995)
"Alma bluntly told his wayward son that repentance could not come unto men except there were a punishment. The punishment may, for the most part, consist of the torment we inflict upon ourselves. It may be the loss of privilege or progress."
A foot note to Elder Packer's printed conference address says: "Forgiveness will come eventually to all repentant souls who have not committed the unpardonable sin (Blasphemy against the Holy Ghost; see Matt. 12:31). Forgiveness does not, however, necessarily assure exaltation, as is the case with David."
See D&C 132:38-39:
"... and in none of these things did he sin against me save in the case of Uriah and his wife; and, therefore he hath fallen from his exaltation, and received his portion; and he shall not inherit them out of the world, for I gave them to another, saith the Lord"

According to Joseph Smith, David will not be forgiven unless he goes through hell first, but he will not be left there:
"A murderer, for instance, one that sheds inocent blood, cannot have forgiveness. David sought forgiveness at the hand of God carefully with tears, for the murder of Uriah; but he could only get it through hell: he got a promise that his soul should not be left in hell.
Although David was a king, he never did obtain the spirit and power of Elijah and the fullness of the Priesthood; and the Priesthood that he received, and the throne and kingdom of David is to be taken from him and given to another by the name of David in the last days, raised up out of his lineage."
(See Teachings of the Prophet Joseph Smith, p. 339:)
See also Ps. 16:10; Acts 2:25-27;

Here are a few quotes by some other general authorities on the subject: President Marion G. Romney (April 1979)
"David, on the other hand, though highly favored of the Lord (he was, in fact, referred to as a man after God's own heart), yielded to temptation. His unchastity led to murder, and as a consequence, he lost his families and his exaltation (see D&C 132:39)."

President Milton R. Hunter (April 1971)
"Having an understanding of the plan of salvation and a thorough knowledge of the seriousness of the gross sins of adultery and murder which he had committed, King David in anguish cried out unto the Lord: "... thou wilt not leave my soul in hell." (Ps. 16:10.)

Spencer W. Kimball(October 1980)
"Perhaps one reason murder is unforgivable is that having taken a life, the murderer cannot restore it. Restitution in full is not possible. Also, having robbed one of virtue, it is impossible to give it back."

Joseph F. Smith(Gospel Doctrine p. 434)
"But even David, though guilty of adultery and murder of Uriah, obtained the promise that his soul should not be left in hell, which means, as I understand it, that even he shall escape the second death."

Martha, The way I see it, a person who sheds innocent blood "shall not have forgiveness in this world , nor in the world to come"(D&C 42:18). The refusal of forgiveness refered to here means that the murderer can not repent and receive forgiveness through the atonement of Christ. They can not be forgiven in the sense that celestial salvation is made available to them. They will go to hell to be punnished for it. However, a person may eventually be able to receive another type of forgiveness which requires paying the price by suffering in hell for the murder. Then they may be able to be rescued from hell, as in the case of David, and still obtain some degree of glory(but not exaltation) after the final judgement, depending on how good they were during the rest of their life.