Well David wrote
"Surely I was sinful at birth, sinful from the time my mother conceived me."[Psalm 51:5]
Here's a different translation: “Behold, I was shapen in iniquity, and in sin did my mother conceive me.” (Psalm. 51:5 KJV)
Nothing there regarding David being a sinner. A strong case can be made that this is talking about the defilement of David’s mother because she was previously the wife of, or the concubine of, a heathen king. David had two half-sisters named Zeruiah and Abigail (1 Chron. 2:13-16). The father of David’s half sisters was not Jesse but Nahash (2 Sam. 17:25). Nahash was an Ammonite king (1 Sam. 11:1; 1 Sam. 12:12). David’s father was Jesse, not Nahash, but David’s half sisters were daughters of Nahash. This could explain why Nahash showed kindness toward David (2 Sam. 10:2).
David’s mother was most likely the second wife of Jesse. The first wife of Jesse would have been considered superior to his second wife, as his second wife had been either the concubine or wife of a heathen king. This would explain why David’s half brothers viewed themselves as superior to David, and why David was considered prideful for thinking he was as good as them (1 Sam. 17:28-30). This may explain why David was not called before Samuel the prophet amongst the other sons, as he was viewed as the embarrassment of the family and possibly was an illegitimate child (1 Sam. 16:11). David’s mother apparently had a good relationship with the Lord (Ps. 86:16; 116:16). But she would have been, in the eyes of Jewish law, considered defiled by her previous relationship with an Ammonite (Num. 25:1,2; Deut. 7:3,4; 1 Kings 11:2-4, Ezra 9:2; Neh. 13:23,25; 2 Cor. 6:14-17).
It may simply be that David’s mother was not married to Jesse when she became pregnant, or that she was still the concubine of, or married to, Nahash the heathen king when she conceived. The context of David’s prayer of repentance in Psalms 51 is not consistent with David making an excuse for his adultery by saying, "I was born a sinner. It’s not my fault. I was born this way." In true repentance, an individual takes full responsibility for their sin and offers no excuses or justification. David was not blaming his sin on his birth.
Then he wrote "Even from birth the wicked go astray; from the womb they are wayward, spreading lies.Their venom is like the venom of a snake, like that of a cobra that has stopped its ears,that will not heed the tune of the charmer, however skillful the enchanter may be."[Psalm 58:3-5] So, we are born sinners and when we grew enough to put it into action, we sinned.
Born sinners but NOT until we sinned? When does that happen, exactly?
An infant will take things they know are not theirs, and that is stealing.
How can an infant have any moral culpability?
They will tell you a big honking falsity to keep from getting their 'bum bum' heated, and that is lying. When they get mad, they will slap, scratch, scream, bite, because they did not get their way. Babies are not the 'sweet little angels' ppl make them out to be. My wife and I do not have kids, but I've been around enough nieces and nephews to know, see and feel their hatred when things do not go their way.
Infants do not speak. Babies are reliant upon their parents and caregiving adults. How are they responsible for their actions?
Well, they do know from their parents what is right and what is wrong.
Perhaps we are speaking past each other? My position is infants do not know "right from wrong." As such they are immune from blame, or guilt, or shame.
They know that if they get caught, to try to lie or deflect the blame to someone else to keep from getting into trouble.
When does a person have self-awareness? When would a person understand 'right from wrong?' And more importantly, how would anyone be able to determine it?