The apostle John defines sin as the breaking of the law (I John 3:4). Paul states that the effect of sin is death (Romans 6:23). He also shows that both sin and death have been a factor in human existence since the start (Romans 5:12-14). The inescapable conclusion is that God's law, His definition of right and wrong, has been in effect since the very beginning! Because His law was in effect, God has ascribed sin to man from the beginning. Without law, there would have been no sin, and thus no death.
The apostle makes it clear in the next verse that sinning in the "absence of law" brings about the same penalty as sinning with full knowledge of the law.
