I don't doubt it. He has some good investigators. I'm sure he had them look into the judge.
His investigation for all those who apply for jobs with his companies have given him a deeper investigation than the government
To really understand what Trump is doing, you have to reverse the process:
1. He has his core platform: wall, deportation, cessation, rule of law, reform. Halt judicial activism, restore basic constitutional rights, etc.
2. He therefore has his team of crack investigators identify, locate & research key FACTUAL elements that support this agenda. It can be any & everything, domestic & foreign.
For example, it isn't necessary that the Mexican judge is hearing his case; it could be ANY Mexican judge hearing any random US citizen's case. In this regard, DT actually got lucky, because he's able to personalize the issue.
3. Once he's got the rock solid facts locked in, then his creative team begins the process of script development. Since it's designed to sensationalize, it's as provocative as possible. So much so that people who don't understand what is occurring really believe that "he's really done it this time - he's gone to far".
4. DT (and his media cohorts who benefit from the increased ad revenues) then reap the whirlwind of controversy, once again dominating the news cycle.
5. Then, just when defeat looks most imminent (and the concern trolls are screaming bloody murder), the long pre-established facts are first dribbled out to establish an initial beach head, by which time the main force lands to begin the counter-onslaught.
6. Because Trump had the particular case dead-to-right long before he laid his chips down, he takes the entire hand. It wasn't even a fair bet. In essence, he's the house, and he wins every time.
Note: HRC's team has got to know this is happening. So what will be their defense? The cannot allow DT to win every single week.