Yes, the basement door is off the foyer next to the half bath, and the house is a closed floor plan traditional colonial. The young people were in the kitchen/dining area and easily could have missed someone coming in the front door and heading straight down to the basement. Zillow has realtor photos.
We should keep in mind that absolutely no one in or around the house saw John's body on the lawn after Karen was supposed to have left him there to die. And that's quite a few people, not including any unrelated passing traffic. It was late and snowing but Fairview is a fairly busy double yellow lined road. The three in the car that pulled up behind her saw her alone in the car with no John in or around her car. All of the guests that walked by the phantom body claimed they were either looking at the ground or the sky as they walked by. Matt McCabe's headlights (he drove right by the "body on the lawn") should have illuminated the area near the flagpole, but nope, the four occupants in his car saw nothing.
Lucky the plow guy should have seen a body as well. He testified he was in the biggest of all the plow trucks with high level lights and didn't see anyone on the lawn. On one of his passes he did see an SUV parked on the street (a no-no after 1 am in the winter in Canton) blocking his view of the area where John was later found. The speculation is that was either an Albert vehicle or Caitlin (sp?) Albert's boyfriend's car. (The Alberts had told police their daughter had left much earlier in the evening but we found out at trial this was a lie and her boyfriend came to pick her in the middle of the night.)
My guess is (and the defense implied through the questioning of Lucky) that the SUV illegally parked on the street during a storm was there to block the view of anyone driving by or any camera from picking up the view of two men moving John's body from the basement bulkhead in back to the area 12 feet from the curb, tossing a shoe on the lawn to make it look like a vehicle hit John before he'd had a chance to enter the house. And of course, if Read had actually hit John, the person who put the SUV there absolutely should have seen John's body.
The only logical conclusion from all this testimony is that John's body was placed on the lawn hours after Read left. Which would also explain why his body temp was still so high when he was found.