The Gospel Intervention
I think the story of Jesus and the woman caught in adultery is a great snapshot of the good news.
The teachers of the law and the Pharisees brought in a woman caught in adultery. They made her stand before the group and said to Jesus, "Teacher, this woman was caught in the act of adultery. In the Law Moses commanded us to stone such women. Now what do you say?" They were using this question as a trap, in order to have a basis for accusing him.
But Jesus bent down and started to write on the ground with his finger. When they kept on questioning him, he straightened up and said to them, "If any one of you is without sin, let him be the first to throw a stone at her." Again he stooped down and wrote on the ground.
At this, those who heard began to go away one at a time, the older ones first, until only Jesus was left, with the woman still standing there. Jesus straightened up and asked her, "Woman, where are they? Has no one condemned you?"
"No one, sir," she said.
"Then neither do I condemn you," Jesus declared. "Go now and leave your life of sin."
The first thing a careful reading will reveal is that Jesus never rebukes the questioners in this particular instance. He knows their wrong motivation (to trap him with the question), but their proposed reasoning for the judgment of the woman is sound -- Mosaic law allowed the stoning of adulterers. So legally speaking, the keepers of the Law were well within rights to execute the woman. (One sticky overlap at this time might have been Roman law, though, which may have disallowed Jews the authorization of capital punishment. But for this particular scenario, that historical interjection is neither here nor there.)
What the Pharisees didn't foresee was that the Teacher they were trying to trap was the Giver of the Mosaic law Himself.
Who knows what Jesus was writing in the sand? Commentators speculate. I think one good guess is that he was writing down all those questioners' secret sins. But the passage doesn't say, so maybe I shouldn't either.
What you have on one side of this woman is the Law doing its job and on the other side of her is the Lord demonstrating his authority over it. The point of this story is not that the woman's sin was nothing, or that her sin didn't deserve condemnation, still less is it that she hadn't done anything wrong. Notice that in that last verse Jesus acknowledges she has sinned and tells her to cut it out.
The point of this story isn't even that the Pharisees were hypocrites. (That point is evident in plenty of other stories, though.) No, the point of the story goes like this:
1. Because of God's good law, our sin requires condemnation.
2. Because only one Man is above the law, all of us deserve this condemnation. ("For all have sinned . . .")
3. The difference between the condemnation of the Law and the freedom of the Spirit is Jesus. ("Therefore, there is now no condemnation for those in Christ Jesus.")
To sum up: The Law is good because it is honest about us being bad. The news is good because it sets us free from what our being bad deserves.
So I don't see a lesson about hypocrisy or "casting stones" or anything like that at the forefront of this much-quoted story: I see the Gospel unplugged. I see sin deserving death and Jesus giving rescue. What a great image of our own salvation this story is!