Is a white lie sinful even if you do it to save another person's life?

For example a man is being chased by mobsters and this man came to your doorstep and pleaded for shelter from the mob because they're going to kill him and then the mobsters come to your doorstep asking if he's there and you said "No he's not here" is that really considered a sin? I mean wouldn't the alternative (aka telling the truth) lead to greater harm for that other person? esp. if it was a friend or loved-one i don't think one would hesitate to protect them from those who would do them harm