In the beginning God was the Word and the Word was in the garden. It is written that there were two rivers: the Tigris and Euphrates Rivers. They existed in the Garden of Eden. A crime was committed there. Why has no one been there to investigate? Genesis 2:14-16 records the first crime on earth.
There is no need for anyone to investigate the first murder, the murder of Abel. God knew immediately who murdered Abel (Gen. 4:1-15). No police, detectives, members of the Federal Bureau Investigation (FBI), members of the CIA, or anyone else were there, and they were not needed. God knew who committed the crime since He is all-knowing. God knew that Cain murdered Abel. That is why the Bible has recorded the victim and the murder. Since God is righteous and holy, we can trust God’s judgmental decision as well. Cain was punished appropriately for his crime. He was no longer allowed to see God, and He was denied access to the Garden of Eden. God was the righteous judge and exacted the correct punishment.
Therefore, no one is needed to investigate the murder. In fact, no one today can investigate the murder since it occurred at least 6,000 years ago.