KANSAS CITY, Mo. – In the end, it wasn’t a fingerprint or a blood-spatter that led authorities to the woman suspected of strangling a mother-to-be and cutting the baby from her womb.

It was an 11-digit computer code.

Police zeroed in on Lisa Montgomery in the most 21st century of ways, by trolling computer records, examining online message boards and – most importantly – tracing an IP address, 65.150.168.223, to a computer at her Melvern, Kan., home.

“That in and of itself led us to the home,” Jeff Lanza, an FBI spokesman here said of the IP, or Internet protocol, address – the unique number given to every Internet-connected computer.

Investigators say that just before the slaying, Ms. Montgomery had corresponded over the Internet with the victim, Bobbie Jo Stinnett, about buying a dog from Stinnett. The same technology that makes instantaneous communication possible enabled authorities to crack the case in a matter of hours and rescue the premature baby.

Ms. Montgomery, 36, made a first appearance yesterday before a packed courtroom in Kansas City, Kan., where her attorney refused to waive her right to preliminary and identity hearings. Both hearings have been scheduled for Thursday morning. Ms. Montgomery is charged with kidnapping resulting in death. Her attorney, Charles Dedmon, would not comment after the hearing.

Assistant U.S. Attorney Terra Morehead also declined to comment, but authorities have said Ms. Montgomery confessed to the crime. The 4-day-old girl was released from a hospital in Topeka, Kan., yesterday. “When we received her, she was in pretty good shape,” said hospital spokeswoman Carol Wheeler. “She is just a beautiful, beautiful baby girl.”

The suspect’s husband, Kevin Montgomery, said he knew nothing about his wife’s alleged actions. He has not been charged with any wrongdoing.

“My family has suffered a tragedy, but I am not the only family,” he said. “I sure hope they get as much support from their church and community as I have, because we are all going to need it.”