I would agree that the sentence is extreme given the circumstances, however just a few points;
I won't go into my thoughts on the value of life vs. the value of possessions, since it's something I've hashed out before.
Are you sure the home owner was motivated by defense of property when he opened fire? If I were awakened to find multiple people had broken into my house while I was still in it I would likely react like a cornered animal; so his motive quite likely was self defence made in a panicked state.
I will say that trying minors as adults defeats the purpose of the distinction, in my mind, particularly for a first offender.
Yes and no. I agree with young offender laws in most cases, but crimes which involve violence or where a person could reasonably foresee that violence could occur should allow for the courts to consider trying one as an adult if they are close enough to that age. Alternately they could still try the person as a minor, but allow for heavier sentences even though dealing with a minor.
Also, that all criminals involved in a crime would be responsible for each other's actions rather than each responsible for their own only is ridiculous.
Not really. I suspect the same principle applies when a person with a few drinks in them gets behind the wheel and kills someone. The idea is that the person is engaging in a behaviour that they ought reasonably to know can spiral out of control. Certain crimes like robbery, B&E...etc have the possibility of spiraling out of control at the victims expense regardless of the intentions of the mildest perpetrator. Nobody promises the victim of a crime proportional consequences, so I think the idea is to transfer some of the risk to the perpetrators. The intent is to start sending a strong message to certain individuals that their actions could spiral out of control with dire consequences.
Consider this. Many a muggings result in one of the muggers violently beating the victim, even if the other muggers just wanted the wallet. If we can hold all parties responsible, the hope is that the mildest muggers may look at the craziest and say "Hey Crazy is unpredictable and I don't want to risk being dragged down with him" and refuse to go along. Crazy on the other hand might be too much of a coward to do it without backup and perhaps may do something else with his evening.
Will that always work? Probably not, but it should work in some cases.
Frankly even accounting for that, the law is ludicrous. It sounds a product of a society that favours vengeance over rehabilitation, to me.
Is it vengeance for vengeance sake or deterrence? I can't speak for hard-core criminals, but up here in Canada impaired driving started to drop when they started taking it more seriously. Now granted it is hard to isolate the cause of this drop since there was a combination of tougher sentences and awareness campaigns, but to date I hear more people saying "I don't want to lose my licence" than I hear people saying "I don't want to hurt anybody" which indicates to me at least that the possibility of tougher sentences can act as a deterrent.
I would agree that the 55 years seems a wee bit excessive, but I can't disagree with the principle behind the felony murder laws.