What if the man lied about ... (spoiler)

What if the rapist lied about being a serial killer? I wanted to throw this possibility out here. I mean, only after hearing that the man had killed several women before, did Farrah agree to call the police. Because she was certain that a killer would be locked up forever and would never come back to stalk her. Now, if the man was smart, he might have figured out that Farrah would react this way. So, when in police station, he would switch back to his original story that he was really innocent and had come up with the killer-confession only to get out of that house.

We, the viewers, don't know if he was really a killer. It's possible that he wasn't. Judging by his behavior at the gas station, it seems likely that he had raped before. But let's say that he had been very careful to get rid of any incriminating evidence at home (because his home would definitely be searched by the police). In that case he should be fairly certain that he would not be convicted of any rape, nor the attempted rape of Farrah. Because none of these things can be proved.