NFL Commissioner Roger Goodell (Jason Decrow/AP)

THERE WAS an almost palpable sigh of relief from National Football League officials after an investigation led by former FBI director Robert S. Mueller III concluded that league officials were not lying when they said they saw the devastating Ray Rice video only when it was publicly shown. But the finding that NFL officials didn’t have access to this key bit of evidence is hardly a vindication. It is a damning indictment of the league’s incompetence in handling this case and its indifferent attitude toward domestic violence.

A 96-page report released last week dissected the league’s handling of the Feb. 15 incident in which the former Baltimore Ravens running back assaulted the woman who is now his wife in the elevator of an Atlantic City casino. Mr. Rice was initially given a two-game suspension by NFL Commissioner Roger Goodell. But when the graphic video of Mr. Rice cold-cocking Janay Palmer hit the Internet, the public uproar caused the Ravens to cut ties with Mr. Rice and Mr. Goodell to indefinitely suspend him; the latter punishment was subsequently overturned in arbitration. Mr. Mueller was commissioned by the league to do a review after the Associated Press reported that league officials had earlier access to the in-elevator video.

After exhaustive efforts — including the collection and analysis of millions of documents and an extensive forensic review — investigators made a fairly convincing case that the league did not receive the video prior to its public airing. But it’s also clear from the report that that was true only because NFL officials made so little effort to obtain the tape.

Moreover, NFL officials shouldn’t have had to see the video to treat the Rice incident more seriously. They had been told soon after that “it was horrific” and it “shocked the conscience.” They also had seen a video taken outside the elevator of a limp Ms. Palmer being dragged by Mr. Rice. “DV [domestic violence] is DV . . . I don’t care who started the incident,” was the telling assessment of one NFL official who had looked into the matter.

Instead of recognizing that a serious assault had occurred and insisting on an in-depth investigation, league officials treated it as a minor dust-up and took actions to minimize the impact on Mr. Rice, the Ravens and the league’s image.

Mr. Goodell acknowledged even before the graphic video surfaced (but in the face of great public criticism) that he “didn’t get it right” in handling the Rice case. He toughened the league’s personal conduct policy, including stricter punishments to deal with players accused of domestic violence. Mr. Mueller’s report recommends a series of steps to strengthen how investigations are conducted. If NFL officials are serious about this incident being a wake-up call, they will move quickly to put those changes in place.