Why it's possible:
- If there was anyone Mrs. DiLaurentis would want to protect the innocence of, it would be Jason. Plus, Mr. Hastings seems to be covering up that night too, and Jason is his son.
- Jason was part of the N.A.T. Club and was in danger after Ali threatened to leak the videos she'd stolen.
- He doesn't remember the night Ali disappeared. There was even a point where he thought he might have killed Ali.
Why it's not:
- Um, remember when "A" drops Jason down an elevator shaft? Not really something you would want to inflict upon yourself.
- "A" has killed one other member of the N.A.T. Club. Jason may hate the girls and Ali, but he has no reason to want to kill Garrett.
Source: ABC Family