The psychiatrist doesn't make any determinations. They simply fill out the paperwork and send to the the FAA where a flight surgeon will look it over and determine whether or not you pass.
That's not entirely accurate. This may get slightly semantical but I'll do my best to explain it.
1.) Applicant gets flagged for tier 2 from MMPI scores outside the norm (commonly people think they failed, they didn't).
2.) The applicant is forwarded to the VHT (virtual hiring team) to complete the packet for regional flight surgeon review.
3.) Once packet is completed the regional flight surgeon reviews your packet and either denies or approves you to receive a psychological evaluation.
4.) If approved, your packet is sent to HQ in Washington D.C.
5.) Your packet will be reviewed by D.C. BEFORE you even get an evaluation to make sure you're eligible.
6.) D.C. will coordinate an appointment with a local forensic psychologist.
7.) You'll do an evaluation including 2-4 tests and a one on one interview.
8.) The psychologist will make a recommendation to the FAA on to approve/deny/seek further tests.
9.) Psychologist in D.C. reviews EVERYTHING and will ALSO make a recommendation. They are not the deciding factor.
10.) Recommendation from D.C. is sent back to the regional flight surgeon. 99% of the time whatever is recommended is what the VHT/regional flight surgeon will do. I.e., if D.C. says you're not fit then you likely won't get a medical.
Where people, like myself, get held up the most is at step two. Gathering ALL the information D.C. wants.
Once my process concludes I will be putting together a litteral guide on how to have your packet ready the first go around. Might even do a flow chart. People love pictures.