Blake Allison, one of 10 relatives of victims who won a lottery for tickets to witness the arraignment of the confessed Sept. 11 mastermind Khalid Sheik Mohammed and four co-defendants, told the New York Post he has told the defendants' lawyers he would testify against executing them.
Even if they're convicted, Allison, a critic of capital punishment, said the defendants should not receive the death penalty.
"The public needs to know there are family members out there who do not hold the view that these men should be put to death," Allison told the Post.
"We can't kill our way to a peaceful tomorrow."
Allison's 48-year-old wife, Anna, was a software consultant who was on her way to visit a client in Los Angeles when her plane, American Airlines Flight 11, was crashed into World Trade Center Tower 1.
Allison, a 62-year-old wine company executive who has remarried, said he had opposed the death penalty for decades before his wife's death.
An Episcopalian, he said he believes it's wrong to take a life.
"First and foremost, I don't think it's right to take a life," he said. "It's grounded in my religious faith. The New Testament is very clear about this."
The Sept. 11 attacks killed nearly 3,000 people.