That's not the right way to look at it; every life is sacred. There is no intrinsically "innocent," "good," or "bad" person. Neither-good-nor-bad people make mistakes and are to be adjudged and punished according to the nature of transgression and their full rights, dignity and sanctity to be restored. The only case where someone can lose any right permanently is for someone who wrongly blames a chaste woman of immoral conduct. Such a person is labelled as untrustworthy and loses the right to testify again in any such case (difference of opinion exists).
It is rather the "justness of the cause" that determines whether a life can be taken.
Say to them (O Muhammad!): 'Come, let me recite what your Lord has laid down to you: (i) that you associate nothing with Him; (ii) and do good to your parents; (iii) and do not slay your children out of fear of poverty. We provide you and will likewise provide them with sustenance; (iv) and do not even draw to things shameful - be they open or secret; (v) and do not slay the soul santified by Allah except in just cause; this He has enjoined upon you so that you may understand; (6:151)
Richard C. Foltz, writing on animal rights in Islam:
There is a subtle, if rarely explored, undertone in Islamic law that
killing in general is essentially a bad thing. Muslims are not allowed
to kill any living thing while in a state of ritual purity (ihram),
for example while praying or on pilgrimage. This would seem to
indicate that killing itself is seen as an impure act, to be avoided
if possible, though such a sweeping connection has rarely been drawn
As for the test cases:
- Someone who is currently trying to kill someone.
Unless the killing itself is for a just reason, and there is no alternative, it is commonly understood as a just reason to exercise violence.
- Someone who has committed murder for no good reason.
The law shall determine - Shariah prescribes capital punishment, forgiveness or blood-money.
- Someone who has had homosexual sex.
The law shall determine - Shariah according to many prescribes capital punishment, but this position isn't uncontested.
- Someone who has unsuccessfully attempted to smuggle a large amount of illegal narcotic drugs from one country to another.
The law shall determine. Indonesia and Saudi Arabia have capital punishment for this case, Pakistan does not.
- A woman or man who has harmed the namus (ناموس, honor) of her or his family.
If a transgression was made (adultery), the law shall apply. Honor-killing has no place in Islam.
- Someone who has paid taxes to the wrong government.
How is that even possible, do you mean ISIS?