According to the Associated Press, Lacy said Tuesday she was moved to act because Karr was seen paying particular attention to a 5-year-old schoolgirl while under surveillance in Bangkok, a situation she called the "turning point for everyone."
"We felt we could not ignore this," Lacy said. She also said a forensic psychologist had told authorities that Karr "was dangerous," and perhaps "escalating" toward an assault or worse.
Prosecutors spent at least $9,300 on investigating Karr and bringing him to the U.S. after he refused to take a more sophisticated DNA test that could have ruled him out as a suspect, Lacy said.
"The decisions were mine. The responsibility is mine, and I should be held accountable for all decisions in this case," Lacy said. She added later, "John Karr inserted himself into this. I don't have a great deal of sympathy for John Karr. I have sympathy for his family."
On Tuesday, a judge ordered Karr sent to Sonoma County, Calif., to face five misdemeanor charges of possession of child pornography from 2001. Local authorities also said they want to examine his computer again for more illicit images.
If convicted, Karr faces a year in prison for each count. The extradition, which NBC News says Karr is fighting, must occur by Sept. 13. For now, the 41-year-old is being held in a Boulder jail.