The most catastrophic "drunk driving" case in U.S. history ended with a whimper this week as the U.S. Supreme Court slashed the punitive-damages award in the 1989 Exxon Valdez case from $2.5 billion to $507.5 million.

Bloomberg reported June 25 that the high court, on a 5-3 vote, ruled that the original jury award was excessive under maritime law.

The oil tanker Exxon Valdez spilled 11 million gallons of oil into Alaska's pristine Prince William Sound after running aground; Capt. Joseph Hazelwood was later found to have been drunk and away from his post at the time of the accident.

In the Supreme Court's decision, Justice David Souter said that the accident was caused by recklessness, not intentional wrongdoing, and that punitive-damages in such cases should roughly equal compensatory damages. The ruling means that the 33,000 commercial fisherman and other plaintiffs in the case will receive about $15,000 each in punitive damages.

Dissenting from the ruling to cut the damages award, Justice Stephen Breyer wrote that, "The jury could reasonably have believed that Exxon knowingly allowed a relapsed alcoholic repeatedly to pilot a vessel filled with millions of gallons of oil through waters that provided the livelihood for the many plaintiffs in this case. Given that conduct, it was only a matter of time before a crash and spill like this occurred."

Exxon Mobil maintains that the spill was a "tragic accident," and the Supreme Court split 4-4 on the question of whether the company could be punished for Hazelwood's misconduct. (Justice Samuel Alito recused himself from the case because he holds Exxon stock.)

Experts noted that the damages award represents about half a day's sales for Exxon Mobil, which recorded a record $40.6 billion profit last year.