A man was sentenced to 102 years in prison Friday for using chloroform and a stun gun to knock out and then rape three teenage daughters of his friends, fellow members of a close-knit Taiwanese community.

Chien Tai Wu, 50, who initially dared police to prove he was a serial rapist, pleaded guilty in November to charges of rape, attempted rape, felonious assault, aggravated burglary and illegal use of a minor in nudity oriented material.

Authorities said Wu volunteered to watch his friends' homes and pets while they were on vacation and later used their garage door codes and keys to enter the homes and rape their daughters.

"It is the position of the state that the defendant should go away forever, and I mean forever," said prosecutor Joe Deters.

Hamilton County Common Pleas Judge William Mallory Jr. gave Wu the maximum sentence.

"I don't understand how you could befriend people, break into their homes and commit these atrocious acts on children," Mallory said.

Because of the drugs, some victims did not remember being raped, thinking they had dreamed it, prosecutors said. But one teenager woke up during an attack and later identified Wu.

Wu, who holds a doctorate in computer science, was arrested in July. Detectives found thousands of child pornography images on his computer, including videos that showed a man breaking into the homes of teenage girls, knocking them unconscious with chemicals and raping them, prosecutors said.