Genesis 4:11

And now art thou cursed from the earth, which hath opened her mouth to receive thy brother's blood from thy hand;

1. The LORD ceased to wait for Cain to admit what he did, and went ahead and described for Cain what the consequences of his actions would be.
2. When dealing with misbehavior in children it's not necessary to wait forever for them to confess. If they don't, get on with the consequences, but let them know you know what they've done (assuming you do).
3. Cain was cursed from the earth. (I'm not sure what that means. He doesn't say "by", so it's not the earth issuing the curse. It's more like some distance will be created between Cain and the earth. Perhaps some benefit previously provided by the earth will be withheld.)
4. The LORD assures Cain He knows what has happened.
5. The LORD likens the ground to the earth's mouth. He speaks of the earth as a living thing.