Actually for the one time DUI > 5 years ago in which the BAC exists and was 0.149 or less, the AME can make the determination and issue.
However the challenge rate is 100%
So when I do that I already have a CADC evaluation in the FAA's DSM 4 format (Have you ever in your life, not just in the past 2 years....per DSM5),
The arresting officer's essay of behavior
A non self indicting personal statement full of detail
All "states of past licensure" certified DMV searches.
I am pretty good a reading personal statements the way the FAA does. You'll note the concurrent string in which I did not feel I could help the guy because of his lack of insight.
I read one a decade back when I was doing FAA:
"My GF and I decided to go over the ridge to visit with a friend of ours so we got on the Harley. after about 90 minute as it was a hot day we stopped at a roadside bar and each had a beer. We continued on. Near the summit, we stopped for lunch and had two each more... We were pulled over about two miles past the bar and the officer asked if we'd been drinking. I was truthful and only blew 0.10......" I didn't bother to read the rest of the essay.
Well, the problem: Truthiness, and can you pick out the other problem?
So when I issue one of them I have to be convinced that there is no possibility of abuse, nor of tolerance, nor of lifestyle centered around the usage, nor of blackouts nor withdrawal.
And a Cert'd. Alcohol and Disease counselor who remembers DSM 4 has to agree with me. In writing, so I can defend it.
So, for the one-timer the question is misuse vs abuse, though you can have dependency on a single offense. For the two timer the question is abuse vs dependency
Bruce