In 1992, a Washington Post-ABC News poll found that 92 percent of blacks — and 64 percent of whites — disagreed with the acquittal of the Los Angeles police officers involved in the videotaped beating of a black man, Rodney King.

“What’s striking is just how constant these attitudes have been,” said Carroll Doherty, the director of political research for the nonpartisan Pew Research Center in Washington.

In Pew polls, black mistrust of the police and courts is far more pervasive than it is toward other institutions. However, a Pew poll taken earlier this year suggests that African-Americans under age 40 — the demographic that made up most of the people who took to the streets in Ferguson in August — are much less likely than their elders to believe that racism is the main force blocking blacks’ advancement.

That whites and blacks disagree so deeply on the justice system, even as some other racial gulfs show signs of closing, is perhaps not as odd as it seems. Decades of changing laws and court decisions mean that the two races now work together, play sports together, attend school together. But they frequently go home to separate worlds where attitudes and experiences toward the police and courts not only are not shared, but are not even understood across the racial divide.