Why does the Torah insert the word "ha'Ganav"?
Sanhedrin, 72a: To teach us that the the same Din will apply even if the Ganav is found entering the house via the roof, the courtyard or via an enclosure, and the Torah only mentions a tunnel because it is the most common. 1
According to another Berasisa in Sanhedrin, Ibid., the Torah mentions a tunnel because the fact that he entered via a tunnel serves as his warning, and no other warning is required, as opposed to where he enters the roof, the courtyard or via an enclosure, where he must be warned before one may kill him. See Torah Temimah, note 5.
Why is one not Chayav for killing the Ganav whom he catches tunneling into his house?
Rashi (citing Rava in Sanhedrin, 73a) and Rashbam: Because it is obvious that the Ganav is desperate and that he will not hesitate to kill 1 anyone who catches him in the act. 2 (He comes ready to kill or to be killed - Rashbam).
Yoma, 85a (citing R. Yishmael): He has no value
What are the implications of the words "ve'Hukah u'Meis ... "?
Sanhedrin, 72b: It implies that whoever finds him
Why does the Torah not obligate whoever finds the Ganav tunneling to kill him like it does a murderer (as Tosfos points out in Sanhedrin, Daf 73a)?
Oznayim la'Tirah: Because: Because it is not absolutely certain that he will kill the owner if he catches him. 1
See Oznayim la'Torah who discusses the difference between R'shus and Chiyuv and between the owner and anybody else who catches the Ba ba'Machteres.
What are the connotations of "Ein Lo Damim"?
Rashi: He is like someone who has no blood, and killing him is therefore not considered murder. 1
Targum Yonasan: Whoever kills him is not guilty of shedding innocent blood.
Sanhedrin, 72b: Refer to 22:1:2:1. And one os permitted kill him even on Shabboa
Why does the Torah discuss specifically tunneling into a house?
Da'as Zekenim: Only then, the Ganav is ready to kill the Ba'al ha'Bayis. One who enters through the door [or window - Hadar Zekenim] plans to flee via the door [or window] if the Ba'al ha'Bayis comes.