Why didn't Jesus cast the first stone?

In John 8:1-11 a woman was caught in the very act of adultery and the teachers of the Law and the Pharisees challenged Jesus, asking him, "Teacher, this woman has been caught in the act of adultery. Now in the Law, Moses commanded us to stone such women. So what do you say?" (John 8:4-5). Jesus stooped down twice to write something on the ground. What he wrote isn't stated, but whatever it was, the woman's accusers left one by one from the eldest to the youngest (John 8:7-9). Only Jesus and the woman were left. Then Jesus stood up and said to her, "Woman, where are they? Has no one condemned you?" She said, "No one, Lord." And Jesus said, "Neither do I condemn you; go, and from now on sin no more" (John 8:10-11).

Why didn't Jesus cast the first stone? First, the text reveals that Jesus wasn't a witness to the crime in question so according to the Law, Jesus wasn't allowed to throw the first stone (Deut. 17:7). Second, this situation was really just a setup (John 8:6). For instance, where was the man that had to be present during an act of adultery? Why wasn't he arrested too? There also had to be at least two verifiable witnesses (Deut. 17:6; 19:15; Matt. 18:16). A rational person would have asked if these witnesses were complicit in the crime for there to have been a thorough investigation. (Deut. 19:18-19)?

Jesus never declared that this woman wasn't an adulteress. He never declared her innocent. However, as we review the situation, we also see that there was not a substantiated case against the woman, especially when there wasn't a single witness left! So, Jesus, according to the Law, should not have cast a stone at all. What Jesus did do was to call the woman to repentance: "Neither do I condemn you; go, and from now on sin no more" (John 8:11).