Skimming the wikipedia page the Jury's acquittal sounds reasonable as the murder wasn't premeditated.
The guy is trivially guilty of killing somebody (enough evidence + admission) but just because somebody killed somebody doesn't mean they are guilty of any specific law (i.e. driving while intoxicated or in this case premeditated murder). You do still need to charge them for the proper law.
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IIUC, the US gets around this problem by just trying people for multiple crimes at the same time and the jury can render verdicts on each of them.
The guy is trivially guilty of killing somebody (enough evidence + admission) but just because somebody killed somebody doesn't mean they are guilty of any specific law (i.e. driving while intoxicated or in this case premeditated murder). You do still need to charge them for the proper law.
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IIUC, the US gets around this problem by just trying people for multiple crimes at the same time and the jury can render verdicts on each of them.