Gregory Peck as attorney Atticus Finch, a small-town Southern lawyer who defends a black man accused of rape, in a scene from the 1962 movie "To Kill a Mockingbird." (AP Photo)

“A court is only as sound as its jury, and a jury is only as sound as the men who make it up,” Atticus Finch, the lawyer in “To Kill a Mockingbird,” tells the jury in his closing arguments. Finch has just convincingly argued to acquit a black man, Tom Robinson, who was falsely accused of raping a white woman in a small Alabama town. Atticus Finch demonstrates for the jury that Tom could not have committed the crime. But the jury of 12 white men vote to convict Robinson, anyway.

Harper Lee, the author of "To Kill a Mockingbird," passed away at 89 today, leaving behind a massive legacy. Her book sold more than 40 million copies since it was published in 1960, and Americans rank it among the most influential books they've read. But after more than 50 years and millions of classrooms lessons, some of its central lessons still, at least at times, go unheard.

Research suggests that the same racial prejudices that led to Robinson's conviction are thriving, if in more subtle ways, in courtrooms today. Numerous studies show that black defendants are more likely to be convicted of crimes than white defendants, and that people found guilty of murdering white victims are significantly more likely to be sentenced to death than those who murder blacks. In one study at Cornell, researchers found that defendants with more stereotypically black features – a broad nose, thick lips and darker skin – were more likely to receive a death sentence in crimes against a white victim.

These differential results have a lot to do with a lack of diversity on judicial benches and juries, which tend to be disproportionately white, male and older, as the jury in "To Kill a Mockingbird" was. Though racial discrimination in jury selection is illegal, it has a long history in the U.S. Research has long suggested that the selection process is biased against minorities, women, the young, the poor, and those with particularly high or low education levels.

An 1880 decision by the Supreme Court prohibited judges and lawyers from striking or selecting jurors solely because of their race – though it allowed exclusions for other factors, like age or education. However, the decision also decreed that juries didn’t have to be racially diverse or representative of the broader population. It rung in a long tradition in which attorneys excluded minorities from juries, but came up with other reasons for doing so beyond race.

When a jury is selected today, the judge will first strike jurors he or she deems incapable of being impartial. Then lawyers for both the prosecution and defense can ask that a certain number of jurors be removed, a practice called peremptory challenges.

As Adam Benforado describes in his book, “Unfair: The New Science of Criminal Injustice,” peremptory challenges were meant to give lawyers the freedom to detect and eliminate subtle, preexisting biases against their clients that might influence the outcome of the case. Instead, the practice is often used to introduce more bias into the system.

A 2011 study that looked at 173 death penalty cases in North Carolina found that peremptory challenges were used to remove blacks from juries at twice the rate of whites. In Houston County, Alabama, 80 percent of the African Americans qualified for jury service were removed from juries between 2005 and 2009 using peremptory strikes.

Though the Supreme Court ultimately ruled that attorneys need to be able to offer a race-neutral reason for barring a juror, in practice it’s been easy for attorneys to come up with a laundry list of reasons to exclude people, like not making sufficient eye contact, working in the same kind of industry as the defendant, or having a family member who has been accused of a similar crime, according to Benforado. Judges are not well-equipped to decide which of these reasons might actually be based on race, and which are not. As Benforado points out, people often use race-neutral terms to justify racist actions or beliefs outside of the courtroom as well.

The result, Benforado argues, is that the justice system has yet to deal with the core problem of discrimination in the courtroom.

This same practice may have at work in “To Kill a Mockingbird.” As Scout, the little girl who is the book's main character, sits in the courtroom, watching her father argue in favor of Robinson, she describes the all-white jury. The 12 jurors were from out of town, “sunburned” and “lanky.” They all seemed to be farmers, Scout says in the book, “but this was natural: townsfolk rarely sat on juries, they were either struck or excused.”

Washington Post book critic Ron Charles explains how Harper Lee will be remembered. (McKenna Ewen/The Washington Post)

See also:

Photos show what crime looks like before it happens

The forgotten way African Americans stayed safe in a racist America

The U.S. court system is criminally unjust