McCaskill, as chairwoman of the Senate subcommittee on consumer protection and product safety, led a blistering round of questioning of GM Chief Executive Officer Mary Barra last week. In an appearance on ABC's "This Week" show, McCaskill said GM now faced "a real moment of truth" as it pursues an internal investigation of the ignition switches and the automaker's response to the problem.
At least 13 people were killed in accidents caused by switches that shut down cars. In 2006, GM changed the faulty part but did not change its identifying part number, which McCaskill said showed an intent to deceive.
Asked on Sunday if someone should go to jail in the matter, she cited a 2010 Supreme Court ruling that said the government cannot restrict political donations by corporations.
"You know we had the Citizens United case where our Supreme Court said corporations are people ... but if in fact they are people, there needs to be some criminal accountability depending on what the facts of the investigation show," McCaskill, a Democrat, said. "I know the Justice Department is taking a hard look at this."
Another member of the subcommittee, Republican Senator Kelly Ayotte, said GM's actions amounted to criminal deception.
McCaskill also joined those calling for GM to establish a victims' compensation fund.
"Now it's time for them to come clean, be transparent and most of all make all victims whole no matter when this deadly ignition caused heartbreak in their families," she said.