570 Baby Irene

Alfred found out several points that afternoon pertaining to the case of Samantha's parents. It would seem as though detective Bo never took it seriously. He never looked at possible motives. He immediately concluded it was a robbery. There was no single documentation on the evidence box to suggest that the Zhaos were even questioned, not once. 

The newly assigned investigator, Di Xue was quick to act on the case, following onto Alfred's suggestion. 

She was told to check on the establishments nearing the crime scene. There was no surveillance ever recorded, but the nearby restaurants or offices may have. She was then told to question the Zhaos and see how they would react about the investigation being reopened.

Also, there was a question about the will. Why would Samantha's parents die after the reading of the will?

The car which they used was a rented vehicle, not even the car company was questioned. This was also part of Alfred's instructions.