DNA from a rape victim's aborted fetus was used to arrest her attacker last week in Upper Darby, said police Superintendent Michael Chitwood.

Samuel Nyenka, 26, was arrested for allegedly raping his girlfriend's 19-year-old sister, who was sleeping in the guest room of the couple's home on Nov. 9.

Police never got initial DNA swabs from the victim because she did not report the rape until four months after it happened, Chitwood said.

"She was concerned it would destroy any relationship she had with her sister, who seemed to be in love with this guy, and she wondered who would believe her," he said.

The victim came to police when she realized she was pregnant and knew that no one else could be responsible, Chitwood said.

Detectives found her very credible but when they twice questioned Nyenka, he vehemently denied having any sexual relations - consensual or otherwise - with the victim, police said.

"It was a question of he said, she said," Chitwood said.

After discussing it with the Delaware County District Attorney's Office and after receiving the permission of the victim, police obtained a search warrant for the fetus she had earlier aborted.

DNA results from the fetus were compared with a DNA swab previously taken from Nyenka and he was found - with 99.99 percent certainty - to have fathered the fetus, police said.

When the results came through last week, Nyenka was arrested at his Sherbrook Boulevard home and charged with sexual assault, rape and related offenses. He remained in county prison on $50,000 bail.

"This is one of the more sensational cases we've seen," Chitwood said. "It just goes to show how the technology of DNA has expanded the investigative process."