Another applicable passage is Romans 5:12-13:

“Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned – for until the Law sin was in the world; but sin is not imputed where there is no law.” (NASV)

A.T. Robertson, Southern Baptists’ foremost Greek authority, commented on Romans 5:13:

“Until the law (acri nomou). Until the Mosaic law. Sin was there before the Mosaic law, for the Jews were like Gentiles who had the law of reason and conscience (Romans 2:12-16), but the coming of the law increased their responsibility and their guilt (Romans 2:9). Sin is not imputed (amartia de ouk ellogeitai). Present passive indicative of late verb ellogaw (-ew) from en and logoß, to put down in the ledger to one's account, examples in inscription and papyri. When there is no law (mh ontoß nomou). Genitive absolute, no law of any kind, he means. There was law before the Mosaic law. But what about infants and idiots in case of death? Do they have responsibility? Surely not. The sinful nature which they inherit is met by Christ's atoning death and grace. No longer do men speak of ‘elect infants.’ ”

Millard Erickson, 2002 president of the Evangelical Theological Society, commented on infants dying in infancy:

“The current form of my understanding is as follows: We all were involved in Adam’s sin, and thus receive both the corrupted nature that was his after the fall, and the guilt and condemnation that attach to his sin. With this matter of guilt, however, just as with the imputation of Christ’s righteousness, there must be some conscious and voluntary decision on our part. Until this is the case, there is only a conditional imputation of guilt. Thus, there is no condemnation until one reaches the age of responsibility. If a child dies before becoming capable of making genuine moral decisions, the contingent imputation of Adamic sin does not become actual, and the child will experience the same type of future existence with the Lord as will those who have reached the age of moral responsibility and had their sins forgiven as a result of accepting the offer of salvation based upon Christ’s atoning death. The problem of the corrupted nature of such persons is presumably dealt with in the way that the imperfectly sanctified nature of believers will be glorified.”
(From Christian Theology, second edition, page 656)