Because 2nd degree murder involves killing someone during the course of committing a felony, and he didn't do that since as a physician he has the right to administer medication. There was no intent to harm the victim, so it isn't murder.
That is only one prong that could bring second degree. The defendant doesn't have to be committing another felony. That is just one instance where they can be charged.
I do think they could have charged Murray with second degree but I do understand that would be a harder case to prove.
Second Degree Murder Laws
Murder is the unlawful killing of a human being, or a fetus, with malice aforethought. There are two types of murder: murder in the first degree and murder in the second degree. In order to bring murder charges, the victim must die within a year of the crime causing his death. Murder is defined in Penal Code Section 187.
Murder of the second degree is similar to murder of the first degree, except the element of premeditation does not have to be proven.
All that is required is subjective awareness on the part of the defendant that his conduct is dangerous to human life. Second degree murder is such a killing without premeditation, as in the heat of passion or in a sudden quarrel or fight.
Malice in second degree murder may be implied from a death due to the reckless lack of concern for the life of others (such as firing a gun into a crowd or bashing someone with any deadly weapon). Under California law, the penalty for second-degree murder is life imprisonment without the possibility of parole.
Depending on the circumstances and state laws, murder in the first or second degree may be chargeable to a person who did not actually kill, but was involved in a crime with a partner who actually did the killing or someone died as the result of the crime. For example, in a liquor store stick-up in which the clerk shoots back at the hold-up man and kills a bystander, the armed robber can be convicted of at least second degree murder.
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