So an officer's life is worth more than a plain old citizen. Interesting take.
Killing a police officer carrying out their lawful duties is a worse crime than killing a civilian and it needs a worse punishment. It's not that the officer's personal life is worth more but the arm of the law they represent is. Killing a police officer is an attack on all of us, on civilization itself, not the officer personally. It calls for immediate and permanent removal from the gene pool. The intention is to deter other criminals from trying their luck. 90% of criminals don't really mind doing time in jail, else one visit would be enough. Jail isn't enough.