This question seems kind of vague. Are we talking about saving someone's life? Are we talking about saving someone from some jail time that they would be serving for a crime that they, themselves, committed? If it's the latter, no. If they did something wrong, then justice demands that they make restitution for their crime. If it's the former, then yes, I would. And then I'd confess to my crime and let our imperfect justice system deal with me as is deemed necessary. I've had a very strong belief in justice lately. Probably all that time I spent training with Batman last summer.