Two old friends I'd known in back in high school got caught doing this.
It was like something out of a bad TV show--or Trailer Park Boys.
One guy was presented with a paternity suit, and his buddy tried to "help" him get out of it (with a semen sample? urine sample? I can't remember.) Anyway, they got caught. I was embarrassed for, and ashamed of them.
I agree with Allifunn that you do not necessarily know these things until faced with the situation. I am terrible at lying.
If it was something like the courtroom drama in Fried Green Tomatoes, I think I could indeed intentionally lie, or attempt to.
Or what if I knew the person I was protecting had *not* done the crime?
Just this past month I have read of two different innocent men, both of whom did long hard time in prison for crimes they did not commit, who were only released after DNA results proved their innocence.