This sounds pretty specific. The State can't file again.
The Supreme Court curbed this discretion in Blockburger v. United States. The Court said that the government may prosecute
an individual for more than one offense stemming from a single course of conduct only when each offense requires proof of a
fact the other does not. Blockburger requires courts to examine the elements of each offense as they are delineated by statute,
without regard to the actual evidence that will be introduced at trial. The prosecution has the burden of demonstrating that each
offense has at least one mutually exclusive element. If any one offense is completely subsumed by another, such as a lesser
included offense, the two offenses are deemed the same, and punishment is allowed only for one.
Murder Reduced to Manslaughter
Generally, murder is defined as the unlawful killing of another with malice, while manslaughter is the unlawful killing of another
without malice. However, in certain situations a charge for murder (either first or second degree) can be reduced to the lesser
crime of manslaughter. In Hawaii, the charge can be reduced if the killing was committed under the influence of an extreme mental
or emotional disturbance.
I don't see how manslaughter would be based on any facts not also included in the already acquitted charge of 2nd Degree Murder. Same course of conduct, same set of facts, same crime essentially.
If the State AG appeals this as he said he will, he's wasting our money, IMO.
I'm not a lawyer, but it seems like there is wide agreement across many lawyers that double jeopardy attaches unless the charges are fundamentally different. Murder and manslaughter are essentially the same except for one additional element for murder: malice.
Had the AG not included manslaughter as a lesser included charge in trial #2 and only charged 2nd Degree Murder, does anyone thing he could come back and refile manslaughter charges for the same crime? Of course not. The fact manslaughter was included in the trial as an option is irrelevant, regardless of the jury being deadlocked. You shouldn't be allowed to include lesser charges as a "shoehorn" around the Constitution to refile if the primary charge is dismissed.