I have argued in the past, mainly in the context of the financial crisis, that the country has been poorly served by the Justice Department’s unwillingness to hold to account big shots like Angelo Mozilo, the former chief executive of Countrywide, whose companies’ illegal practices helped lead us to the brink of financial apocalypse. It has sent a terrible message that there are two kinds of justice: one for the rich and powerful, and another for everybody else.

But there is another reason corporate executives need to be prosecuted when corporate crimes take place. It sends a signal to every other executive about what is — and is not — acceptable behavior. The threat of prison can change a culture faster and more effectively than even the heftiest fine. If, after the Texas City explosion, one BP executive or more had been prosecuted, it seems to me quite likely that the Deepwater Horizon accident would never have happened. A prison sentence would have done the thing that all those fines never did: force the company to begin paying attention to safety.

Prison is what makes the difference. Otherwise, it’s only money.