Let's not confuse the issues or the evidentiary burdens in this case. The only intent the prosecution must establish is the intent to cause death. The act must follow "deliberation", but malice is not an element of the charge:
“
Colo. Rev. Stat. § 18-3-102(1) A person commits the crime of murder in the first degree if:
(a)
After deliberation and with the
intent to cause the death of a person other than himself, he causes the death of that person or of another person...”
The prosecution does not bear the impossible burden of proving the null hypothesis, that it WASN'T second degree murder heat of passion. Prosecutors need to prove, based on the evidence taken as a whole, ONLY the above elements of the charge. Motive, means, and opportunity are helpful to understand what happened but missing pieces of the mosaic of evidence are not a problem for the prosecution if the pieces the jury sees present the picture required by the statute. Other WSers have repeatedly articulated the evidence supporting the charge and I will not repeat it here.
And let's understand what heat of passion murder is, and who generally asks for the instruction. If the evidence shows that the victim's serious and highly provoking act provoked an irresistible passion that caused the defendant knowingly to kill, the sentence is mitigated from Class 2 to the Class 3 Felony range. It is the defense, not the prosecution, that would seek an instruction on this issue, and it is very difficult for the defense to argue in the BM case because they'd have to admit BM killed SM, and show all the mitigating circumstances, below.
Colo. Rev. Stat. § 18-3-103(1) A person commits the crime of murder in the second degree if the person
knowingly causes the death of a person.
...
(b) Notwithstanding the provisions of paragraph (a) of this subsection (3), murder in the second degree is a class 3 felony where the act causing the death was performed upon a
sudden heat of passion, caused by a serious and highly provoking act of the intended victim, affecting the defendant sufficiently to excite an irresistible passion in a reasonable person;
but, if between the provocation and the killing there is an interval sufficient for the voice of reason and humanity to be heard, the killing is a class 2 felony.
Would the jury consider SM to have committed a "serious and highly provoking act" by wanting to leave her marriage and taking steps to do so? I doubt the defense could even be allowed to argue for this. And there is ample evidence that this was not a situation where she hit him with a baseball bat, and he immediately grabbed it and beat her to death. Assuming her expressions of intent to leave met the provocation test, there was plenty of time between those actions and his response for the voice of reason and humanity to be heard.
All JMO, of course.