This is a story about three people (A, B a C) crossing a desert. A hated C and decided to kill him - he poisoned the water in his sack (only C had water). B also wanted to kill C (not knowing that the water of C had been already poisoned) and so B made a hole into the sack of C and the water spilt out. A few days later C died of thirst.
Who was the murderer - A or B?

Well, this is a hard one. In my opinion, there is no clear solution. Each point of view is correct, somehow. Most of the people would say that A is the murderer. Solicitor of B would stress 2 things:
1. to take away poisoned water from someone does not mean killing him,
2. B just made C live longer, even if he did not mean to (the poison might have killed C earlier).

However, solicitor of A could present the following argument:
"How can be A be punished for committing a murder by poisoning C, if C did not swallow a single drop of poison."

It is morally clear that both A and B are guilty of homicide attempt. Legally, 2 different courts could judge them in 2 different ways. And logic gives us the opportunity to write a whole book on this topic.