He isn't but he is suggesting he would give them his eyewitness testimony in exchange for safety. Learning that Steve would so easily sell her out forces Judy to realize that they were never in this together. Steve was selfish and didn't want the complication of an accident in his life, so he told her to keep going — likely because any kind of investigation could have revealed that he was laundering money. He forced Judy to live all that time wracked with guilt over something that he quickly compartmentalized as "we hit a deer."