The legal theories regarding homicides have changed a lot, but there has not always been some kind of distinction between the attempt and the result. It's the distinction between an assault with a deadly instrument and the resulting killing. And not all jurisdictions look at things the same way! The aspect of killings under the aspect of Law in History is a very interesting question:
Republican Roman Law dictated to torture all slaves of a killed landowner to find out if any of the slaves were in league with the killer because Law dictated slaves were needed to be tortured so their testimonial was admissible in court. And then, all that were found to have not protected their owner could be summarily executed1. The very same state also said that not all killings were equal: Killing your own father or close relative was seen as more heinous and was punished by a more cruel death than killing your neighbor while inflicting death upon your own slave was without punishment, slaying someone's else slave was a civil dispute where you destroyed a thing.1 But Roman law did not have murder per se, only homicide, which was defined by the intent and the item used - it didn't matter if you did succeed at once, or if he died later from the wound:
On the other hand the Roman law had but one crime of this
nature, viz., homicidium (with its aggravated form of parridicium or
slaying of a relative) and this originally .was purely a crime of intent.15Hunter, Roman Law, 1069
Thus, fatally wounding another with a sword was homicidium; but
striking him with an .iron key was not, even though the result should
prove equally fatal. 16Justinian's Digesta, XLVIII, VIII, I, III.
Negligence resulting in death is mentioned as early as the Twelve
Tables, but not as a crime, nor was it visited with a serious penalty.
"One who slays another accidentally," it is declared, 19XII Tables, VIII, 24 "shall provide a ram to be sacrificed in his stead."
The same document quoted here also shows some insight in other areas where the distinction between different types of killings comes from, for example in Japan:
Chapter XXVI of the Japanese Penal
Code treats of (intentional) homicide which may be given capital
punishment.37Japanese Penal Code, Art. 199. But Chapter XXVIII covers "involuntary (accidental) homicide" which is "punished with a fine not exceeding one thousand
yen."38ld. .Art 210.
This refers to the Japanese Penal Code, which also lists in the 1960 edition:
Article 199 A person who kills another shall be punished by the death penalty or imprisonment with work for life or for a definite term of not less than 5 years.
Article 201 A person who prepares for the commission of a crime prescribed under Article 199 shall be punished by imprisonment with work for not more than 2 years; provided, however, that the person may be exculpated in light of circumstances.
Article 202 A person who induces or aids another to commit suicide, or kills another at the other's request or with other's consent, shall be punished by imprisonment with or without work for not less than 6 months but not more than 7 years.
Article 203 An attempt of the crimes prescribed under Article 199 and the preceding Article shall be punished.
Here we see that murder is not defined. Just "you kills somebody, you get punished" under 199, 201, 202, or 203. Attempt here is apparently punished just like the deed itself, even preparing a killing is a crime.
A totally different approach has modern Germany under StGB 211, prescribing always life in prison as the sentence for the done deed. As it is a Verbrechen to commit murder, the StGB 22 does make it's attempt punishable, in principle also with the same punishment. However, the judge can use StGB 23 Abs. 2 to lessen the punishment to 3-15 years as StGB 49 dictates, and total incompetence (like... attempting to stab somebody to death with a rubber knife held between the teeth while having the feet tied together) can allow to not punish at all or any other lesser sentence under StGB 23 Abs 3. But Germany also has a single article in its Grundgesetz, which carves out a hole in the normal laws:
(4) Gegen jeden, der es unternimmt, diese Ordnung zu beseitigen, haben alle Deutschen das Recht zum Widerstand, wenn andere Abhilfe nicht möglich ist.
(4) All Germans shall have the right to resist any person seeking to abolish this constitutional order if no other remedy is available
This has been discussed as possibly including a carte blanche to murder of a dictator, but so far hasn't been invoke ever.