ABC's failure to contact authorities about a father beating his teenage daughter before airing it on "Primetime" last week prevented any criminal prosecution in the case, the prosecutor who could have pursued those charges said on Tuesday.

The girl, Kyle Nelson, appeared on "Good Morning America" Tuesday to say she had forgiven her father for the incident. But she asked the network not to run tape of the beating again and ABC News agreed.

With the family's consent, ABC taped hundreds of hours of interaction between the Nelsons of Lake Placid, N.Y., for a story on stepfamilies. On Friday night it aired tape of an argument during which Kyle's father, Joe, lunged at her, slapped her, then punched her five times while kneeling atop her.

More than 2,000 people have e-mailed "Primetime" about the incident. Among the "horrified" viewers was Derek Champagne, Franklin County district attorney, where the family lives. He said he knew nothing of the incident before it was shown on TV.

Because the beating took place in December 2002, Champagne said he's prevented by the statute of limitations from prosecuting the case. ABC News gambled by not allowing professionals to assess the family's situation, he said.

"It is clear that intervention from 2002 through to the present could have benefited everyone in the Nelson family," he said. "It is fortunate that while the aired tape was sitting on an editing shelf, further tragedy did not occur."

ABC News said there was no other such incident in more than 1,000 hours of tape it had collected on the Nelson family. The family included Joe, a correctional officer and military reservist who has served in Iraq since the taping, Kyle's stepmother and three younger children. Joe and the stepmother both acknowledged on tape they had struck Kyle on other occasions.

"I don't think we did the wrong thing," said David Sloan, executive producer of "Primetime." "We spent a long time on this. We consulted experts. We looked at it ourselves, and looked at the totality of the circumstances and we didn't see anything egregious."

None of the experts consulted by ABC News recommended contacting outside authorities, Sloan said.

"I think it should have been reported," said Jim Hmurovich, president of Prevent Child Abuse America, a Washington-based organization. "They had some evidence that some potential child abuse was going on. I don't think the law gives common lay people, so to speak, the ability and discretion to decide what is child abuse and what is not."

Kyle Nelson, now 18, appeared with her mother and maternal grandmother on "Good Morning America." She moved in with her grandmother soon after the incident caught on tape.

Nothing like that had happened before or since, and she doesn't think it will happen again, she said.

"My dad was just torn up about it, the day it happened," she said. "I just feel really bad that people have gotten so angry. I'm not going to condone what he did, but at the same time I have forgiven him. He does love me, there's no doubt about that. He's definitely proven that a lot of times."

Kyle's mother, who ABC did not fully identify, said she was angry at her ex-husband.

"I didn't realize until this all came out how bad it really was there," she said. "But I know he loves her."

A psychologist interviewed by Diane Sawyer, Patricia Papernow, scolded ABC for showing the tape so many times on Friday — at least three times. Sloan said there are no plans to show it again.

"She thought it was not therapeutic," he said, "and we stand corrected."

The 105-minute "Primetime" was seen by 8.1 million people on Friday, above the newsmagazine's season average of 7.3 million, according to Nielsen Media Research. Ironically, ABC had preceded the show with a 15-minute Tom Cruise interview in order to draw more viewers — and only 6.4 million people tuned in to the interview.