The old woman died in the house on the second floor 8 years ago so she was stuck to the floor. So they had to cut the section of floor out around her body in order to take her to autopsy. But they didn't put any framework underneath the floor section that they cut out. Without the support, the floor with the dead woman would have fallen to the first floor damaging the evidence.
Near the end of the show they took the old man back to the house in order to jar his memory so they could find out how his wife died. They let a fragile old man walk up to the second floor by himself when there was a large hole cut into the floor. In real life the Workplace Health and Safety people would be all over that. The old man could have fallen through the hole in the floor. They should have put a solid cover over the hole in the floor.