People who can't be AD because reason...
Let's try to find out who -A can't be with pretty little logic
Emily (too nice)
Hanna (too dumb)
Alison (she is in the show's last scene, I doubt she is A-)
Mona (be there done that (I hope))
Paige (last episode before 7x20)
Jason (last episode before 7x20)
Melissa (Torrey only shot for like two days)
Noel (dead)
Sara (dead)
Charlotte (may not be dead but AD tries to find out who did it)
The Parents (because duh)
Toby (had a car accident when A- kidnapped Jenna)
Ezra (was in Columbia during 7x10)
Jenna (got kidnapped by A-)
Suspects:
Aria (likelihood 5%)
Spencer (5%)
Caleb (20%)
Wren (35%)
Lucas (35%)
Can you add anything