Recent high-profile cases of child sex abuse have roused national revulsion against the adults who perpetrated them. Rarely mentioned is the sobering statistic that more than one-third of the sexual abuse of America's children is committed by other minors.

For many of the therapists and attorneys who deal with them, these juvenile offenders pose a profoundly complicated challenge for the child-protection and criminal justice systems. It's a diverse group that defies stereotypes, encompassing a minority of youths who represent a threat of long-term danger to others and a majority who are responsive to treatment and unlikely to reoffend.

"There's a long continuum, from kids who will never do it again to a kid who probably will be an adult rapist/pedophile," said Steve Bengis, executive director of the New England Adolescent Research Institute in Holyoke, Mass. "It's not a `one size fits all' yet we end out with public policy that's geared toward the worst 5 percent."

That public policy includes a federal law, the Adam Walsh Act, with a requirement that states include certain juvenile offenders as young as 14 on their sex-offender registries. Many professionals who deal with young offenders object to the requirement, saying it can wreak lifelong harm on adolescents who might otherwise get back on the track toward law-abiding, productive lives.

Some states have balked at complying with the juvenile registration requirement, even at the price of losing some federal criminal-justice funding. Other states have provisions tougher than the federal act, subjecting children younger than 14 to the possibility of 25-year or lifetime listings on publicly accessible registries that include photos of the offenders.

Delaware recently had a 9-year-old child on its registry. Several other states have registered 12- and 13-year-olds.

"We're bringing down a very heavy hammer on the head of kids, with significant life-altering consequences," said Marsha Levick, deputy director and chief counsel of the Juvenile Law Center in Philadelphia. "It's a knee-jerk reaction that's foolhardy beyond imagination."

Nicole Pittman, a Human Rights Watch researcher, has been analyzing the impact of registration on the children who get listed, and says states should halt the practice. But she knows it's a longshot quest.

"Most legislators do not believe children should be on the registry _ yet it's the kiss of death for most politicians to vote against any sex offender law," she said.

Basic data about child-on-child sex abuse is detailed in an authoritative, Justice Department-sponsored analysis of crime data from 29 states. Conducted by three prominent researchers, the 2009 analysis found that juveniles accounted for 35.6 percent of the people identified by police as having committed sex offenses against minors.

Of these young offenders, 93 percent were male, and the peak ages for offending were 12 through 14, the researchers found. Of the victims, 59 percent were younger than 12 and 75 percent were female.

The report referred to a popular misconception that juvenile sex offenders are likely to reoffend, and said numerous studies over the years have shown the opposite _ that 85 to 95 percent of offending youth are never again arrested for sex crimes.

University of Oklahoma pediatrics professor Mark Chaffin, a co-author of the 2009 report, says efforts to deal constructively with juvenile sex offenders are complicated by the tendency of some legislators and others to lump them together with adult sexual predators.

"That used to be the message _ that we should apply the template from what we know about adult pedophilia," Chaffin said. "Now that the data has shown most of those assumptions were wrong, it's difficult to undo those messages that people in the advocacy and treatment fields were putting out a generation ago."

Experts say the young offenders differ from adult sex offenders not only in their lower recidivism rates, but in the diversity of their motives and abusive behavior.

While some youths commit violent, premeditated acts of sexual assault and rape, others get in trouble for behavior arising from curiosity, naivete, peer pressure, momentary irresponsibility, misinterpretation of what they believed was mutual interest, and a host of other reasons. Some cases involve sibling incest; sometimes the offenders have autism or other developmental disorders that lessen their ability to self-police inappropriate conduct.

"There needs to be a highly discriminative response system," said sociologist David Finkelhor, director of the University of New Hampshire's Crimes Against Children Research Center. "It needs to differentiate between the kids we should stigmatize as little as possible, who are probably going to be fine with some kind of education, and others who need a lot of intervention, including maybe incarceration, because they pose a tremendous risk."

"We run a big risk if we get it wrong," he added. "We fail to protect the public on one hand, or we ruin the lives of young people who might otherwise be headed in a healthy direction."

In most cases of child-on-child sex abuse, the public never hears about it. Experts say many incidents are never reported in the first place, due to the shame or embarrassment of victims and their parents, and most of the cases that are reported are handled confidentially through the juvenile justice system.

An exception was the highly publicized case of Gabriel Myers, a 7-year-old foster child in Florida who hanged himself in 2009. Post-mortem investigations determined that he had been a victim of sex abuse perpetrated by an older boy, had touched some of his classmates in sexually inappropriate ways, and was on several powerful psychotropic medications.

In response to his death, Florida formed a task force which concluded that Gabriel's problems with sex abuse were not addressed effectively by the long chain of adults who dealt with him. The task force recommended upgraded training about child-on-child sex abuse and development of an alert system to better monitor children with sexual behavior issues.

"With Gabriel Myers, the big thing was lack of training," said Robert Edelman, who has worked with many abused children as a mental health counselor in Gainesville, Fla. He said investigators, counselors and case managers involved with child-on-child sex cases should be required to get special certification.

The ripple effects of such abuse were evident in another case that Edelman became engaged in, involving a man now in his 20s who was molested at age 8 by an older boy, and later _ at 15 _ was charged with molesting his half-sister.

During a counseling session after that arrest, Edelman noticed slashes on the youth's arm _ he'd tried to kill himself out of remorse for abusing the sister.

In his early 20s, the man was arrested for a domestic violence incident involving his wife, Edelman said, and at one stage faced the possibility of having his children removed from the home because he'd been labeled a juvenile sex offender.

"Something that happened to him when he was 8 was still being carried around 15 years later," Edelman said.

Veronique Valliere, a psychologist with a counseling practice in Fogelsville, Pa., has worked with numerous youths implicated in sex offenses, ranging from those she deemed highly unlikely to reoffend to others who posed a clear long-term menace. One such case, she said, involved a youth who began molesting younger children when he was 12 or 13 and was showing signs of developing pedophilia.

"By 14, he was so sophisticated that he could sexually assault a child sitting next to him in church _ or in the backseat of a car," Valliere said.

Despite extensive attempts to treat the young man, the abuse continued, and Valliere said he is now serving a 30-to-60-year prison sentence for child sex abuse he committed as a 22-year-old.

"He was a rare case," she said. "He had every opportunity to get better. We did everything we could do, but he just wasn't willing to manage himself."

Looking nationwide, experts differ as to whether sex abuse by juveniles is proliferating or abating.

The latest juvenile crime data from the Bureau of Justice Statistics indicates that arrests of juvenile sex offenders declined by about 25 percent from 2000 through 2009. That would mesh with a decline in child sex abuse committed by adults, as well as a decline in the overall juvenile crime rate.

But data from New York City, Florida and elsewhere indicates that the prevalence of child-on-child sex hasn't dropped noticeably.

In any case, forms of abuse evolve with the times as sexting becomes a common youth activity and easily accessible online pornography affects some children.

"There's a fear of technology _ parents don't think they can control it," said Marsha Levick, who has been working with colleagues to dissuade prosecutors from criminalizing commonplace teen sexting activities.

For parents, it's often hard to discern warning signs about potentially dangerous sexual activity or to identify youths who might pose a threat to their own children.

"It would be less scary if we could come up with a stereotype ... so as a parent we could say, `Stay away from this type of child,'" said Nancy Arnow of Safe Horizon, a New York-based victim services agency. "There is no typical youthful offender. They come from all backgrounds."

Safe Horizon serves adult victims of rape and sex trafficking, but Arnow said the child-on-child sex abuse cases are among the most difficult.

"We have to distinguish between sexualized behavior that might be pretty normal _ experimenting, touching each other _ versus molesting, subjecting another child to harm," she said. She recalled investigations of children as young as 7, and the arrest of an 8-year-old.

In New York City, sex offenders aged 7 through 15 usually end up in family court, where the main goal is rehabilitation, not punishment.

"We're supposed to consider needs of juveniles and the need for public safety, so it's balancing act," said Thea Davis, chief of the family court's Sex Crimes Prosecution Unit. Cases often end with plea bargaining and probation. The most severe outcome is an 18-month placement in a secure state-run facility for juvenile offenders.

The hardest cases, Davis said, are intra-family cases where a cousin or brother abuses a younger cousin or sibling.

"Immediately you have to separate the perpetrator from the victim and make sure the victim is safe," she said. "But you also have to think that in the long run you're dealing with a family, and you're not going to keep them separated forever."

Virginia White, a family counselor with Pittsburgh Action Against Rape, deals with young victims of sex abuse, including those targeted by siblings.

"The parents are in a tough place _ they feel guilty a lot," she said. "And the victim is often torn, because the other sibling may be removed from home."

Ideally, parents as well as the offending child should be involved in treatment, according to Jay Deppeler, president of an agency called Edison Court in Doylestown, Pa., that runs a residential treatment program for adolescent male sex offenders.

However, Deppeler said stigma and fear of consequences probably deter some families from telling authorities about cases of intra-family abuse.

"The family may circle the wagons, and the abuse may persist," he said.

Another challenging type of abuse cases involves youths who are autistic.

Lawrence Sutton, a psychologist from Pittsburgh, recently assessed 37 youths in a residential sex-offender unit and found that 60 percent were autistic. He said these youths, many of them past victims of sexual abuse, can be treated successfully if the reasons for their behavior problems are understood.

Many don't know who to form relationships, "how to make friends," Sutton said. "Most of them have done to others what was done to them at some point."

Deppeler recalled one autistic young man who came through Edison Court as an outpatient. He had committed a sex offense as a 14-year-old and later _ after turning 18 _ committed a property-related offense that sent him to the adult criminal justice system. As a result, the young man became obligated to apprise prospective employers of his full record, including the juvenile sex offense _ making him "virtually unemployable."

"Long term, I fear his prospects are quite bleak," Deppeler said. "What do we end up doing with a guy like that?"

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Online:

Florida task force report on child-on-child sex abuse: http://bit.ly/sqaEvA

Office of Justice Programs report on juvenile sex offenders: http://1.usa.gov/uUjX82

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David Crary can be followed on Twitter at http://twitter.com/CraryAP