Four years after the death of Laquan McDonald, Jason Van Dyke — the white Chicago police officer who shot the black teenager 16 times — faced his day in court. But in a trial where race was central to the case, there was only one black person on the jury. That’s in Cook County, where nearly a quarter of people are black. How did that happen? And how much does the racial makeup of a jury matter?

Study after study has shown that all-white juries are harsher on black defendants, make more errors, and discuss fewer of the case facts. And all-white juries, like in the case of Emmett Till, have historically been problematic. But they also aren’t a thing of the past.

In the jury selection process called “voir dire,” potential jurors are questioned and lawyers can dismiss jurors with cause for bias.

But each side is also allowed to strike a certain number of jurors without giving a reason — these are called “peremptory challenges.” This is where racial discrimination in jury selection becomes tricky.

Lawyers aren’t technically allowed to use these strikes to dismiss jurors based on race or sex, thanks to legal precedent set by Batson v. Kentucky. In that case, a prosecutor used his peremptory challenges to dismiss all four potential black jurors. The defendants appealed to the Supreme Court and won.

Today, if one side suspects jurors are being dismissed based on race, they can issue what’s called a “Batson challenge.” The judge must decide if a strike is discriminatory and can give the accused an opportunity to come up with a race-neutral reason for the dismissal of a juror.

But the problem is, lawyers have easily worked around this challenge, coming up with race-neutral reasons that still work to dismiss jurors based on race. It’s a strategy so well-known that even this attorney training video lays out how to dismiss black jurors and get away with it. Over the years, studies have shown a striking pattern of excluding black jurors across the country, and Batson has been widely regarded as a failure at keeping discrimination out of jury selection.

Watch the video to learn more about how race factors into jury selection, and why it complicates the prospect of a fair trial by jury.