I have served on three juries--2 criminal and 1 civil. The first one was settled by a plea deal before it went to the jury. The second one, like the first one, had a black male defendant. I was an alternate for that one so was dismissed before the jury deliberated, but I knew one of the other jurors and he told me that a black woman juror was very strong for finding the defendant guilty.
The civil trial involved a black woman suing a company who had fired her, wanting back pay and punitive damages. The company had a black lawyer arguing their case. The jury only had 8 people--one of them a black man. We unanimously found against the claimant in 45 minutes.
My understanding is that, as a general rule, the voting behavior of individual jurors is confidential, and must not be disclosed publicly.
Sometimes, individual jurors sitting on high-profile court cases will come out after the trial and explain how and why they voted the way they did, but to my understanding, it would not be permitted for anyone to be "outed" without their explicit permission.
I thus cannot imagine any large-scale study examining possible racial bias - unless they examine only all-White vs. all-Black juries.
Regards,