Robot

Dr. Susan Calvin:
Detective, the room was security locked.  Nobody came or went.  You saw that yourself.  Doesn't this have to be suicide?Detective Del Spooner: Yep. [drawing his gun] Unless the killer is still in here. [Spooner searches through the robot part as Calvin follows behind]Dr. Susan Calvin: You're joking, right?  This is ridiculous.Detective Del Spooner: Yeah, I know.  The Three Laws.  Your perfect circle of protection.Dr. Susan Calvin: "A robot cannot harm a human being."  The First Law of Robotics.Detective Del Spooner: Yeah, I've seen your commercials.  But doesn't the Second Law say that a robot must obey any order given by a human.  What if it was given an order to kill?Dr. Susan Calvin: Impossible!  It would conflict with the First Law.Detective Del Spooner: Right, but the Third Law says that a robot can defend itself.Dr. Susan Calvin: Yes, but only if that action does not conflict with the First or Second Law.Detective Del Spooner: Well, you know what they say.  Laws are made to be broken.Dr. Susan Calvin: No.  Not these Laws.  They are hard-wired into every robot.  A robot can no more commit murder than a human can...walk on water.