"I thought it did in fact deter crime, but I found out that wasn't true," Ryan said.
It wasn't until Ryan was elected governor did he begin to have second thoughts.
"I was in the mansion with my wife, dinner time watching one of the local Chicago channels and here comes this guy out of prison all smiles and happy," Ryan said.
The guy Ryan saw on TV was Anthony Porter. He was released from prison after several years and eventually exonerated for a double murder. At one point, Porter was 48 hours away from execution.
His case prompted Ryan to call for a death penalty moratorium. On January 11, 2003, Ryan blanket-commuted the sentences of all 167 inmates on death row to life in prison. Four of them were pardoned.
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"My concern basically was if I had left office and didn't do anything about it and woke up one morning and found some innocent person had died, I would have to live with that the rest of my life," Ryan said.
Ryan said his tough decision was made with the help of lawyers like Andrea Lyon. The first woman in the United States to try a death penalty case, Lyon has represented some of the former death row inmates who were exonerated.
"At the end of the Illinois death penalty, we had exonerated 19 people from death row and executed 12," Lyon said. "That's bad for even government work."
Lyon said Ryan's actions caused many other governors nationwide to rethink their positions on the death penalty. Twenty years later, Ryan has no regrets.
"I'm glad I did what I did," Ryan said. "It cost me a few friends but that is the way it is."
In 2011, Governor Pat Quinn signed legislation abolishing the death penalty in Illinois. But Ryan said criminal justice reform has a long way to go in the state.