David is a sinner (Ps 51:3-51:5)

“I know my transgressions.

My sin is ever before me.

Against you,

You alone,

Have I sinned against.

I have done what is evil in your sight.

Thus you are justified

In your sentence.

You are blameless when you pass judgment.

Indeed,

I was born guilty.

I was a sinner

When my mother conceived me.”

David knew that he had sinned. His transgression was in front of him. He knew that he had done evil in the sight of God. He recognized that the sin was against God alone, as he did not see the human implications of his sin. This was evil in the sight of God. Thus God was justified and blameless in passing judgment on him. Then David hid behind the fact that he was born guilty. He was a sinner from his conception. Somehow he was throwing his sinfulness back to his mother and sex in general. Perhaps he was alluding to the human condition to be prone to sin or something akin to human original sin.