12 He that smiteth a man, so that he die, shall be surely put to death.
13 And if a man lie not in wait, but God deliver him into his hand; then I will appoint thee a place whither he shall flee.
14 But if a man come presumptuously upon his neighbour, to slay him with guile; thou shalt take him from mine altar, that he may die.
15 And he that smiteth his father, or his mother, shall be surely put to death.
If you kill someone, you must die. Period. But, if you are acting in self defense, the sentence is still death, but God will provide a place of sanctuary for you. If you stay in the place that He has given for you as a sanctuary, you may survive. If you leave that place, the judges can take hold of you to exact punishment for your crime.
This is only good for self defense, not for sneaking up on someone and executing them.
And, you better NOT kill your parents for ANY reason.
God has provided us a sanctuary in the Lord Jesus Christ today. As long as we abide in Him, our sins -- our CRIMES -- are forgiven!