The command to give no false testimony against your neighbor is important because it was designed to protect people against the predatory practice of malicious witnesses siding against the innocent to reap illicit gain in the ancient world.
But more important than any human court in the Bible is the divine court. In John’s letter to the scattered churches he says that the testimony of God is that he offers eternal life to humanity in the person of Jesus Christ. And Jesus Christ is the advocate who ensures that we receive this blessing from God. The evidence for Jesus’ ability to do this is stated by John to be the water, the blood, and the Spirit. Why? Jesus was endorsed by God the Father at his Baptism. Jesus predicted his own crucifixion as part of his mission. And the Holy Spirit confirmed the Father’s endorsement of his ministry by raising him from the dead. The beauty of such a Tribune testimony is that it means that the offer is a good faith offer to all sinners as well as an offer that remains on the table for Christians. The qualifications of Jesus are why John can so confidently say, “If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.” Jesus testified truly about God and God’s testimony is that he will pardon all who come to him.