Why I'm against capital punishment

A long time ago, I supported capital punishment. I would have conversations with my parents about why it's "necessary." I even created a political cartoon about it for one of my classes. My reasoning was that it would insure that if a murderer was executed, he/she wouldn't be able to kill anyone again.
That was what I believed... until I was going to write an essay about capital punishment. That was the day when I started to question my views. My teacher, who had a degree in Criminal Justice, gave me some facts about the issue that I had never heard before.
I don't know what it was that caused me to be against it. I guess it just sort of... happened. I guess I figured that the bad outweighed the good.
Now I am against capital punishment. The main reason is because I think it's somewhat hypocritical and that innocence should not determine someone's right to live. Even still, many innocent people are killed, which is not a good thing. Besides, with the information I've gathered, there doesn't seem to be any real proof that capital punishment lowers crime rates (another reference can be found here).
From a more practical perspective, capital punishment is also expensive (and not just because of the amount of lives taken away) and according to recent sources, it seems to be more expensive than life in prison.
I also found a really interesting graph about how police chiefs view capital punishment that might be worth reading.
I'd also like to clarify that I don't, in any way, support crime. I just believe in finding effective, nonviolent alternatives to the death penalty that reduce the crime rate. Also, I don't trust the government enough to let them kill people.