Now that we think the captain was legal in Mexico, how about the 20 year old FO? I was flying J3 cubs and cessna 150's when I was 20. This kid is flying right seat in a Lear Jet? What training did he have? I have been there with bending the rules with charter flying so have an idea what they were doing.
If the old guy was asleep the 20 year old probably would have a problem if the autopilot failed because he bumped the yoke. Now he is hand flying with little or no experience. My post about our Lear flight to LAS earlier shows how easy it is to get a Lear out of control if you don't have experience.
Did you notice the Mexican police that came out to the crash site stole a lot of crash evidence and probably cash and were put in jail while they were guarding it? Now we are expecting an accurate accident report? Unlikely.