The case doesn't get anywhere close to double jeopardy. The charges are derived from a crime the took many years to develop through to finality.
The officer, while alive had life and livelihood destroyed by an attempt to end his life. A punishable crime committed against him. He lived on physically impaired and with no posibility of return to active duty or any other skilled occupation. His life was effectively destroyed, though a hope could remain for improvement, somehow.

The time served by the perpetrator of the attempted murder was rightly served. It was not to be expected that he could or would surpass all hope of the victim of the crime and become successful while the victim deteriorated, languishing in his injury from the crime. Therefore, the civil liberty enjoyed by the perpetrator was forfeited in the commission of the crime.

When the officer died, therefore double jeopardy could not apply.

The murderer should spend the remainder of his life in prison without the posibility of parole.

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Adage: 2 things are certain in life; Death & Taxes. Therefore; God & Beelzebub had a meeting to fix the problem. A mighty storm prevailed for ages until finally they ended the storm with the agreement: From now on Anyone whom chooses doesn't have to die. "Everyone wins said Beelzebub. You get an eternally grateful bunch of worshippers praying forever for lower taxes as I goad & prod them forever with higher & higher taxation."