It is clear who they are. One is the person who found the body and has an alibi, who the defense also focused on during the trial. The lot near the house is a bit deceptive when you see the actual lot and the way the houses are arrayed. It's also not a house the person visited.

The other suspect is Adnan's mentor who with Adnan was heard discussing if investigators could identified when the victim was killed after the body was found. .