It wasn’t a good Friday for Laci Peterson’s family and friends.

The results of a DNA analysis revealed by state Attorney General Bill Lockyer confirmed what many already feared to be true — the remains of the adult woman and male infant that washed ashore in Richmond last week were those of the missing Modesto woman and her unborn child, who was to have been named Connor. Further, Modesto police announced that Laci Peterson’s husband Scott had been arrested for the murders of his wife and son.

At this writing, only God and Scott Peterson know with certainty whether the 30-year-old salesman is guilty of the crimes with which he will be formally charged this week. But the very notion raises the question for thinking people everywhere: would a man kill his wife and child, then callously dispose of their bodies in San Francisco Bay? And if so, why?

Our asking these questions presumes that evil is rational, that people must necessarily have “good” (or at least comprehensible) reasons for doing very bad things. By now, we should understand that this presumption is false. Evil requires neither reason nor excuse. Evil is so thoroughly self-absorbed that it finds no cause to explain itself. Evil simply is.

You and I should know this from our own experience with sin. When we commit sin, do we usually have a genuine, inescapable justification? Of course not. We want to do it, so we do. It’s as simple as that. Only later, when we have been confronted with our wrongdoing, do we begin to backfill and hunt for plausible-sounding rationales for the sins we’ve committed. In the moment of wickedness, however, no excuse is necessary. We desire, then we act. And, as Scripture reminds us, “when desire has conceived, it gives birth to sin; and sin, when it is full-grown, brings forth death” (James 1:15).

We can illustrate this truth using Biblical examples of familial misconduct. When Cain, eldest son in humankind’s first family, killed his younger brother Abel, did he have a valid explanation? Was there some legitimate case to be made that Abel had so wronged his sibling that extermination became Cain’s only logical recourse? We know better. The apostle John asks, then succinctly answers, the pivotal question: “And why did (Cain) murder (Abel)? Because his works were evil and his brother’s righteous” (1 John 3:12).

That’s all there is to it, really. Cain killed Abel because Cain was an evildoer. We could delve into the issues of jealousy and shame and sibling rivalry and a host of other psychoanalytical claptrap, but Abel would still be dead—because his brother chose evil instead of good.

In the same way, we could consider the events surrounding David’s children Amnon and Tamar. Tamar was a beautiful young woman whose half-brother Amnon lusted for his sister to the degree that he assaulted her sexually (2 Samuel 13). We read the account with revulsion — a brother would force himself on his sister? Why would Amnon commit so vile a deed? Because, as James said, his desire gave birth to sin. Or, as John summarized it, Amnon’s deeds were evil. Period. End of story.

Whoever murdered Laci and Connor Peterson — whether it was Scott Peterson or some other party yet unknown — did evil. Doubtless many columns, articles and books will be written in an attempt to make sense of these heinous actions. Perhaps some explanation will be identified. Perhaps not. But no justification, no rationale, no grievance either genuine or perceived, will ever carve to the heart of the matter beyond this: Evil is evil. Wickedness is wickedness. Sin is sin. No matter how we try to explain the ugliness, we cannot change its nature.

Hands that shed innocent blood are a hateful abomination to the Lord. But so are proud looks, lying tongues, and hearts that devise wicked plans (Proverbs 6:16-17). Of these, we all stand guilty. And, like the murderer of Laci and Connor Peterson, we are without excuse.