Ann Arbor, Mich.

“IF our laws were broken ... we will bring those responsible to justice,” President Obama pledged on Tuesday, in announcing an investigation of the events leading to the April 20 explosion of the Deepwater Horizon drilling rig. His words may have been, in part, political damage control; efforts to contain the spill remain dire. But federal prosecutors have been working behind the scenes for weeks to determine whether BP, Transocean (the owner of the rig) and Halliburton (the company that did the cementing job on the deep-ocean well) should be charged with crimes.

Now, it’s up to Attorney General Eric H. Holder Jr. to ensure that the legal response to the calamitous oil spill in the Gulf of Mexico is better than the emergency response.

If the spill had resulted from a hurricane or lightning strike, or if it had been an unavoidable accident  an equipment failure that happened without warning  it wouldn’t warrant criminal prosecution. Increasingly, however, it appears that there was negligence or worse in the events leading to the explosion of the rig.

News reports have described warning signs that went unheeded and deviations from standard industry practice: Gas was seeping into the well. The blowout preventer was leaking. Concerns were raised about the well casing. There were signs of trouble with the cement in the well. Mud circulation was limited. A final concrete plug was not properly installed. And when disaster struck, the blowout preventer failed.