What did Brigham Young teach regarding Blood Atonement, and is that doctrine still held today in the LDS/Mormon Church?

I found this article at Desert News concerning the topic:

The Church of Jesus Christ of Latter-day Saints released this statement Wednesday:

In the mid-19th century, when rhetorical, emotional oratory was common, some church members and leaders used strong language that included notions of people making restitution for their sins by giving up their own lives.

However, so-called "blood atonement," by which individuals would be required to shed their own blood to pay for their sins, is not a doctrine of The Church of Jesus Christ of Latter-day Saints. We believe in and teach the infinite and all-encompassing atonement of Jesus Christ, which makes forgiveness of sin and salvation possible for all people.

That same site states the date of this announcement as June 18, 2010.

Is this doctrine still believed today?

The article published by Deseret News on June 18, 2010, clearly states that blood atonement is not a doctrine of the LDS Church. Although this statement is from 2010, I understand that many members and leaders did not believe or teach the doctrine long before that time.

Some confusion over whether this teaching is still believed today may be caused by the fact that some leaders of the church in the 20th century taught that there is a "true doctrine" of blood atonement, in contrast to a "false doctrine" of blood atonement used by critics of the church. In particular Bruce R. McConkie in his book Mormon Doctrine (1966 edition, p. 66, entry on "Blood Atonement Doctrine") stated that "under certain circumstances there are some serious sins for which the cleansing of Christ does not operate, and the law of God is that men must then have their own blood shed to atone for their sins." However, it is important to note that McConkie was censored by other church leaders for his publication of Mormon Doctrine, so in spite of its title, the entry on blood atonement should not be considered authoritative on the subject.

Where is this teaching found?

The best source for Brigham Young's teachings on the subject is the Journal of Discourses, a project that Young's stenographer George D. Watt, as well as 11 other stenographers, worked on. Following is a list of links to sermons where Young mentions blood atonement (all of which can be easily found online in the electronic version of the Journal of Discourses):

• Vol. 1, discourse 19, pp. 103–111, "President B. Young's Journey South—Indian Difficulties—Walker—Watching and Prayer—Thieves and Their Deserts—Eastern Intelligence—Financial State of the Church—Gaining Knowledge, Etc."
• Vol. 2, discourse 32, pp. 179–191, "The Priesthood and Satan—The Constitution and Government of the United States—Rights and Policy of the Latter-Day Saints."
• Vol. 3, discourse 35, pp. 243–249, "Instructions to the Bishops—Men Judged According to Their Knowledge—Organization of the Spirit and Body—Thought and Labor to Be Blended Together."
• Vol. 4, discourse 10, pp. 51–57, "The People of God Disciplined By Trials—Atonement By the Shedding of Blood—Our Heavenly Father—A Privilege Given to All the Married Sisters in Utah."
• Vol. 4, discourse 42, pp. 215–221, "To Know God is Eternal Life—God the Father of Our Spirits and Bodies—Things Created Spiritually First—Atonement By the Shedding of Blood."

What are the specifics regarding the doctrine of Blood Atonement that Brigham Young taught?

In answering this, I draw on the two references in volume 4 above, where Brigham Young seemed to give the most detail on this teaching as he understood it.

Brigham Young taught that there were certain sins that could be atoned for only through the spilling of the blood of man, e.g. from Vol. 4, discourse 10:

It is true that the blood of the Son of God was shed for sins through the fall and those committed by men, yet men can commit sins which it can never remit. As it was in ancient days, so it is in our day; and though the principles are taught publicly from this stand, still the people do not understand them; yet the law is precisely the same. There are sins that can be atoned for by an offering upon an altar, as in ancient days; and there are sins that the blood of a lamb, of a calf, or of turtle doves, cannot remit, but they must be atoned for by the blood of the man. That is the reason why men talk to you as they do from this stand; they understand the doctrine and throw out a few words about it. You have been taught that doctrine, but you do not understand it.

He also taught that carrying out the task of blood atonement was an act of love, e.g. from Vol. 4, discourse 42:

All mankind love themselves, and let these principles be known by an individual, and he would be glad to have his blood shed. That would be loving themselves, even unto an eternal exaltation. Will you love your brothers or sisters likewise, when they have committed a sin that cannot be atoned for without the shedding of their blood? Will you love that man or woman well enough to shed their blood? That is what Jesus Christ meant. He never told a man or woman to love their enemies in their wickedness, never. He never intended any such thing; his language is left as it is for those to read who have the Spirit to discern between truth and error; it was so left for those who can discern the things of God. Jesus Christ never meant that we should love a wicked man in his wickedness.

What sins could be atoned for by the cross of Christ and which could not?

This is a difficult question to answer; I do not believe that Young ever specifically outlined which sins require a blood atonement and which do not. In a couple of his sermons, he outlined specific instances where he felt capital punishment would aid in atoning for sins (e.g., in Vol. 3, discourse 35, with regards to adulterers caught in the act). However, often in these instances it is unclear if he believed the sinners' own blood was atoning for their sins or not.