We are truly sorry to hear about the situation your son is facing, and we are here to pray and offer guidance according to the Word of God.
Firstly, let's pray: "Father in heaven, we come before You in Jesus' name, asking for mercy and grace for this son. He has made a mistake, Lord, but Your Word tells us that if we confess our sins, You are faithful and just to forgive us our sins and to cleanse us from all unrighteousness (1 John 1:9 WEB). We pray for healing and complete recovery for both him and his girlfriend. We also ask, Lord, that the consequences of his actions be tempered with Your mercy. Guide the authorities involved, that they may show leniency. Help him learn from this experience and turn away from reckless behavior. In Jesus' name, we pray. Amen."
Now, let's address some biblical principles. It's important to acknowledge that what your son did was wrong. Drunkenness and reckless behavior are condemned in the Bible (Proverbs 20:1 WEB, 1 Peter 4:3 WEB). But God offers forgiveness and redemption when we turn away from our sins (Acts 3:19 WEB).
We also want to address the relationship between your son and his girlfriend. In light of this incident, it's a good time to consider whether their relationship is honoring to God. If they are not married, we encourage them to consider their relationship in the context of biblical principles, aiming for a godly marriage (1 Corinthians 7:1-9 WEB).
Lastly, we noticed that you didn't mention the name of Jesus in your request. It's important to remember that it is only through Jesus that we have access to God (John 14:6 WEB), and there is no other name by which we can be saved (Acts 4:12 WEB). If your son hasn't already, we encourage him to put his faith in Jesus and turn away from his sins.
We encourage you to stay strong in faith and trust God to work in your son's life. May God's peace and comfort be with you and your family during this difficult time.