Gustave said: "Obviously our eternal destiny is formalized at the point of our death (not prior) so the idea of a judgement of investigation prior to death seems alien (and odd). " This issue is complex and consists of several parts.
* What is sin? Sin might be said to be anything that is in violation of the will of God, whether known, unknown, intentional or un intended. As our spiritual knowledge is limited, it might be said that we are always sinning as we never in this life are fully informed as to God's will for us. We are constantly learning, but never in this life knowing and understanding the totality of God's will for us. This knowledge of God's will for us comes through the agency of the Holy Spirit working in our lives.
* God, in my understanding, only charges us with sin when the Holy Spirit has convicted us on that point, and we in rebellion have decided to go against the leading of the Holy Spirit. None of us know how the Holy Spirit has led in the life of other people. The Bible does not indicate that growth in spiritual life comes in a set of uniform steps that is the same for all people. As an example, I consider my friend Gustave to be an honest follower of Christ. I assume that Gustave does not keep the Sabbath in same sense that I do. On the assumption that my understanding is correct, God is not charging Gustave with sin if the Holy Spirit has not convicted Gustave in the same manner that I believe that I have been convicted.
* How does this relate to what we call the investigative judgment? It does not show that people have come into a total knowledge of God. That will only come in eternity. Rather it shows to all of the created intelligent beings that: 1) The Holy Spirit has reached out to every person. 2) Every person has been given an opportunity to become a dedicated follower of Christ, wherever that might lead. 3) Every person has made a final decision on whether or not to be a follower of Christ. 4) These are the set of people who have made the decision to spend eternity with God. These are the people who have made the decision not to spend eternity with God. 5) Consistent with the SDA understanding, those who decide not to spend eternity with God will be separated from the life-giving power of God which sustains us today and will therefore cease to exist.
* From this perspective, the investigative judgment has a focus on God. It is God who is shown to all created, intelligent life, to be just in the decisions as to giving some eternal life, and it shows that sin will never rise again, as it has been removed from those who have been granted eternal life.