Why might this be at court-martial?

KLDNews13 has a video report of a "Marine accused of fatally stabbing wife on H-3 could be turned over to the military for a court martial (sic)." The H-3 is one of Hawaii's Interstates, from the Honolulu area of Oahu island to Marine Corps Base, Kaneohe Bay. K-Bay, as we call it.

The report says that he is held in custody on second-degree murder charges. The reporter notes that the military has the death penalty. But the death penalty would only be for a conviction under UCMJ art. 118. Hawaii does not have the death penalty. 

The military equivalent of "second-degree" murder does not authorize the death penalty. I think voluntary manslaughter under UCMJ art. 119 is the closest analogy.

The spouse was pregnant, so the possibility exists of a second charge under UCMJ art. 119a at court-martial. Death is not an authorized punishment under this article. 

It does not appear the spouse is a service member.

The report notes (as we know) that civilian and military authorities frequently discuss jurisdiction when a service member is a suspect.

https://www.kold.com/video/2022/08/02/marine-accused-fatally-stabbing-wife-h-could-be-turned-over-military-court-martial/