Psalms 51:5

The king went on to confess the depth of his sinfulness. He had been a sinner from the time he came into existence as a human being, namely, at his conception. This is one of the strongest indications in the Bible that human life begins at conception rather than at birth (cf. Psalms 139:13-16). He viewed sinful acts as the fruit of a sinful nature, not as the product of his environment or the situation that had triggered his acts. This verse does not mean David felt free of personal responsibility for his actions. He felt responsible, as is clear from his statements in the context.