[1]https://en.wikipedia.org/wiki/Stingray_phone_tracker [2]https://en.wikipedia.org/wiki/Parallel_construction
Novel evidence like this is probably unlikely to do well in court for the reasons you describe.
Nevertheless, they imprisoned a man for ten days, and proceeded to press for criminal charges over the course of the year. As described the man had to spend his entire savings on this defense.
The court system worked correctly, in that the judge told the prosecutor to produce more evidence. The charges were dismissed.
So we have the "happy" ending of a man whose life has been turned upside down, whose financial situation has been ruined, and who has had to spend his time and effort defending himself rather than contributing to society in a positive way. All because facial recognition was used as the only piece of evidence.