- Protect victims from their assailants properly.
- Deter violent criminal activity.
Murder, as a crime, is punishable with the harshest sentence: Life imprisonment.
Attempted murder seems to be seen as a less serious offence due to more lenient sentencing, but in many cases; this is simply due to the incompetence of the offender (much to the relief of the victim) to actually kill his target.
Short version; Why? Let's give them the same sentencing guidelines.
Long version: Should this be the case? Isn't it irresponsible to let people get away with a murder they planned but failed in. What if Derek/Derrick Bird missed everyone he shot at? Would you let him out to try it again? If cases involve premeditation of murder, life sentences should be mandatory whether successful in their plans or not.