T:Present some evidence that Scripture teaches that justice demands that death is necessary in order for God to be able to forgive past sins.

M:Tom, the Jews were required to confess their sins upon the head of a subsstitutional sacrifice and then kill it. Pardon could be secured in no other way. God could not grant pardon without the death of a substitute. Death was required to grant and receive the benefits of forgiveness.

Thus says the LORD of hosts:


"Execute true justice,
Show mercy and compassion
Everyone to his brother."

(Zech. 7:9)

Why can't God just freely forgive them without a substutitionary sacrifice? If you have already answered these questions then please forgive me for not recalling.

Let us ask another question, Why did God not pardon the sinner without the sacrifice of Christ? Was it because he did not love man sufficiently? – Ah, no! God is revealed through Jesus Christ. Christ says, “I and my Father are one.” At the crucifixion, both the expression of the divine love and the revelation of the world’s depths of defiant sin came to the climax. But even there Jesus, dying on the cross while the unrepentant world scoffed at its feet, poured forth his soul’s longings for man in these words, “Father, forgive them; for they know not what they do.”
Thus is revealed how God feels even toward an unrepentant world. He longs to forgive them. Why does he not do it? – Such an act would ignore his law and set it at naught, thus leading others to thoughtlessly violate it. But the violation of that law brings as an unavoidable result misery and death. No forgiveness that could not remove these would be worth having. A forgiveness that led more men into them would be a curse rather that a blessing. Every good father has at times felt a desire to grant his child some present pleasure, but has been compelled to forbear, for fear of future pain....

Sin is secession from the government of God. Satan seceded, and sought to exalt his throne above that of God. Sinners are those who have joined themselves to Satan’s forces in the secession. God, in infinite love, sens his own and only Son to put down the rebellion. He cannot pardon those who are still in rebellion, for this would but justify the rebellion and dishonor the law, and so perpetuate and multiply the misery. But through Jesus this rebellion is finally to be put down entirely. “The seed of the woman shall bruise the serpent’s head.” O’er every hilltop of earth and heaven, where for a short time there has waved the black standard of the man of sin, there shall forever float the white pennon of the Prince of Peace.
Every one who lays down his arms and surrenders his opposing will to God has the promise of pardon. This pardon God can grant, and not dishonor his law. Yea, more, it is through this pardon that the mercy and love of God’s law and government are revealed, -- a love that only commanded the right way, not to be arbitrary and domineering, but that men might be happy, -- a love what when men repent of the wrong, and turn back their hearts toward the broken law, is ever willing to forgive the past and give power for future obedience. It is thus that God can be just, and still the justifier of those who believe on Jesus. (God is Love, Fifield)

The life of Christ was not the price paid to the father for our pardon; but the life was the price which the Father paid to so manifest his loving power as to bring us to that repentant attitude of mind where he could pardon us freely. (God is Love)