A man just bought a lie detector robot and he can't wait to try it.
Her 14-year-old son comes home from school 2 hours late.
Father: Are you late, where have you been all this time?
The son: I stayed at school to prepare a homework!
That's when the robot goes to the son and gives him a good slap...
Father: As you see, this robot is a lie detector, and you better tell the truth...
Son: Ok...I was at a friend's house and we watched the movie "The 10 Commandments".
Then the robot gives him a good slap again.
The son: Ok I lied it was a porn movie...
Father: I'm ashamed of you! When I was your age I never lied to my parents!
the robot then goes to the father and gives him a good slap...
The exasperated mother then says: well, decidedly he is as much a liar as you, he is your son...
The robot suddenly turns towards the mother and gives her a good smack... :)