Mormonism teaches about spiritual death in two different ways. They believe spiritual death means separation from God. All people on earth are spiritually dead because they are physically separated from God. The resurrection of Christ is what redeem all people from spiritual death and brings everyone back into the presence of the Lord to be judged.
Mormonism also teaches, “Spiritual death comes as a result of our own disobedience. Our sins make us unclean and unable to dwell in the presence of God.” (True to the Faith, p. 48) Anybody judged unworthy for the Celestial kingdom will experience another spiritual death. They will not dwell in the eternal presence of God, but will be designated to the lower kingdoms of glory.
Biblical Christianity teaches:
Because of the Fall, every person by nature is dead in sin and subject to God’s wrath. (Eph. 2:3-5) The consequences of sin are physical and spiritual death. This means separation from God. No person is able to earn God’s favor or avoid the eternal consequences of sin by their own efforts. Only through God, can a person be rescued from spiritual death and be brought to spiritual life and faith in Christ.