I think this type of thinking is really getting into the minutia of an issue (or non-issue), in an almost dangerous way, about the very personal cognition of individuals. And, I’m skeptical of any real improvements this sort of study provides our society without stepping into the zone of policing of thoughts.
As someone who has been through the criminal justice system — albeit for minor infractions — my experiences show me that police, guards, judges (no interaction w/jurors) treat all detainees, short-term or otherwise with some level of derision, period. That’s kinda the whole point of jail. I haven’t read any reports on this empathy gap thing, but I can imagine there‘d be a litany of factors in how a person reacts to the study, such as personal experiences as a child or young adult, media exposure, environment, parenting, education, region, etc. But then the issue becomes so much more than just one of race.