Isn’t a brief glance at the shape of some congressional districts a smoking gun that it happens all the damn time?
But what we have here is a guy with a bunch of analysis based directly on racial data, and a bunch of emails detailing specific plans and concerns about racial demographics. In this one case we know the relevant boundaries constitute a civil rights crime.
https://www.npr.org/2018/01/14/577969855/gerrymandering-in-m...
(Nor is it the only story NPR has on gerrymandering in Maryland, by the way - merely the most recent one.)