Sanhedrin 72: Killing a Thief in One's Home; How Do We Determine the Intent of a Thief?

A new Mishna teaches us that a thief who is found breaking into one's house may be killed.  One can assume that the burglar plans to kill him for the money and possessions present.  If the thief broke a barrel and blood has spilled, the home owner is not permitted to kill the burglar.  If the thief broke a barrel and there is no blood spilled, he may be killed by the home owner.

The Gemara opens up multiple lines of questions regarding this Mishna.  Perhaps this was a father breaking into his son's home.  The Torah says that if someone seeks to you you, you should kill that person.   But a son should not assume that his father would kill him and cannot kill his father in self-defence.   A stolen item should be returned, but perhaps the thief could not return a stolen item.  Perhaps the barrel was broken unwillingly.  We follow the rabbis' questioning in many directions.

The Gemara suggests that we must be very sure that the burglar is attempting to kill us.  Otherwise we are liable for killing the thief.   Returning to the notion of father and son, the rabbis teach that a father's love for his son is far too great to lead to murder.  A son might not love his father in the same way, however.  They question whether there might be others whom we love so much that we can assume that they would not kill us when breaking into our homes.  

The Gemara mentions three ways of breaking into one's home: tunnelling, though the roof, through the courtyard, or through an enclosed field.  Is our Mishna teaching that a thief can be killed only if he enters the home through tunnelling?  Or was that the most common way of breaking in to a home and thus used as a general example?

What about warning?  In most cases of murder or other serious action against another person, we are required to warn the person that they are transgressing before we stop them in their tracks.  Rav Huna notes that a minor who is about to kill is killed without a warning (minors do not require warnings) and the killer is exempt.  A baby who is likely to kill its mother during the birthing process is killed to save the mother.  Once the baby leaves the womb it is like any other person and we do not kill one person to save another.