The inside of the apartment did not match the outside appearance of the apartment building where the murder took place. On the outside the door to apt. 24 was next to the neighboring apt. door, which means there would be a common wall between the two stretching all the way back to the rear of the building (to ensure structural integrity of the load bearing walls). Inside, there are a couple of steps to a small hallway with a room on each side. All of that would be inside the apartment next door.
There was no sufficient evidence to even charge Peggy for the crime. Aside from the fact there would be no gun powder residue on her hand (to show she fired the gun), there would have been residue of the drug that knocked her out still left in her system. What's more, there would have been no trace of her finger prints anywhere in the apartment, even though this was supposed to be place she had used for a lover's rendezvous for the last several weeks.