Defense lawyers often raise the influence of childhood poverty on defendants' lives when they argue for diminished sentences, yet the jails are full of poor people.

Last week in Texas, a judge actually bought the flip side of that argument, that an irresponsible upbringing stemming from the defendant's affluence made him incapable of good judgment.

Ethan Couch, 16, of Fort Worth, had a blood-alcohol level three times the legal limit for an adult when, while driving his father's F-350 pickup truck 70 miles an hour in a 40-mph zone, he struck and killed four pedestrians who were tending to a disabled vehicle. Two of his seven passengers were seriously injured.

Prosecutors asked for a 20-year sentence. The defense team invoked "affluenza," contending that the teen never had been disciplined by permissive parents, and therefore did not understand the consequences of his actions.

Judge Jean Boyd sentenced Mr. Couch to 10 years of probation, the first part of which will be spent at a $450,000-a-year rehabilitation center in Newport Beach, Calif.

Every person is the product of his upbringing. But as one public defender in Texas put it, his clients tend to suffer from "desperenza" yet never get a break because of it.

The case may not yet be over, but for now it stands as an example of not just the impact of affluence on one teenager, but on unequal justice.