When the state Legislature created Hawaii’s sex offender registry in 1997, proponents argued that the new law would improve public safety and inform residents about offenders living in their neighborhoods.

But little empirical evidence exists today to show the registry actually makes Hawaii’s communities safer.

And the state doesn’t know the whereabouts of roughly 600 offenders on the registry, or 1 in 5, raising more questions about the effectiveness of the system and its ability to track nearly 3,000 convicts.

For more than 150 who have absconded, no photos are available on the online site. Most of the absconded were convicted before the registry law took effect and have not re-entered the criminal justice system.

Carol Plummer, an associate professor at the University of Hawaii’s Myron B. Thompson School of Social Work, used to think the registry was a great tool.

But she says she now believes it provides a false sense of security and misdirects scarce resources. Plummer maintains that the money allocated by the state to run the registry — roughly $150,000 a year for basic expenses — would be better spent on treatment and prevention.

The $150,000 doesn’t include costs for state enforcement actions, equipment maintenance and supplies, and expenses incurred by county agencies that assist with registry duties, including investigations and prosecutions.

"I’ve now come to despise (the registry)," said Plummer, who used to counsel sex offenders and victims. "It does more harm than good."

Proponents, however, say the system does keep communities safer by notifying residents about where offenders live.

With that knowledge, parents can avoid putting their children into risky situations, preventing molestations and other offenses from happening in the first place, according to Laura Ahearn, executive director of Parents for Megan’s Law, a New York-based nonprofit that supports registries.

That kind of benefit won’t show up in studies, Ahearn added. "You can’t prove a negative," she said.

The state attorney general’s office, which oversees Hawaii’s registry, and Honolulu Prosecutor Keith Kaneshiro likewise touted the registry’s tracking and notification benefits, including having information readily available if an offender is suspected in another crime.

"It puts offenders on notice that we’re monitoring them," said Joshua Wisch, a spokesman for Attorney General David Louie, in a written statement. "It also helps us track offenders as they move from one jurisdiction to another."

Kaneshiro wrote, "The purpose of the sex offender registry is to provide notice to the community about an offender’s history and location. I believe it’s important that the public have access to this information, but I don’t know how many people actually make use of it."

While the creation of sex offender registries nationally in the 1990s was driven largely by legislative responses to horrific, high-profile crimes against children, researchers note that most sex crimes tend to be committed by people whom the victims know, not strangers.

Over the past 10 years<$o($)>, for instance, nearly 80 percent of Hawaii’s sexual assault cases were committed by people known to the victims, according to Plummer, citing data from the Sex Abuse Treatment Center. If most victims generally are familiar with their would-be molesters, that significantly diminishes the value and effectiveness of a registry, Plummer and other experts say.

Along those same lines, national researchers largely have concluded that registries have not been proved to make communities safer, though officials often refer to registries as tools to help protect children from sexual predators.

"Ironically, empirical studies indicate that registration and community notification have done little (if anything) to increase public safety," wrote University of Hawaii law professor Carole Petersen and UH public administration professor Susan Chandler in a 2011 paper. "Yet the public continues to support these laws, largely due to misconceptions about the nature of sex offenders, their recidivism rates and the ability of sex offender registration to prevent crime."

Even though Hawaii’s registry has been in place for about 15 years, the AG’s office was not able to show the Star-Advertiser any empirical studies the state had done or commissioned showing the registry was effective in boosting public safety or reducing the recidivism rates of sex offenders.

A 2008 study by several researchers from the University of Arkansas and elsewhere concluded that Hawaii was one of three states in which the introduction of sex offender notification laws contributed to statistically significant decreases in the monthly incidence of rapes. In six other states the researchers evaluated, they found no statistically significant changes.

Local experts, including Plummer, were skeptical of the Hawaii finding.

Wisch, the AG spokesman, said his office gauges the effectiveness of Hawaii’s registry by periodically evaluating statistics on the percentage of noncompliant offenders — those who don’t inform the state of their whereabouts or don’t meet other registration requirements. Failure to comply is a Class C felony punishable by up to five years in prison for each violation.

But a high compliance rate doesn’t necessarily mean communities are safer — it just means many sex offenders are keeping their registry information current, according to therapists who treat them.

And a significant number of offenders don’t abide by the rules.

In Hawaii the state doesn’t know the whereabouts of roughly 600 offenders, either because the offenders failed to provide current addresses or simply absconded, according to registry data. That’s about 21 percent of the 2,900-plus offenders on the list or, viewed another way, a 79 percent compliance rate.

Wisch said Hawaii’s compliance rate has remained steady over the past year, fluctuating between the high 70 and low 80 percentiles. The rate dipped to the high 60s a few years ago when the state started requiring offenders to physically check in with police yearly — instead of every five years — to verify their information and get a current photo taken.

Some states, including Missouri, South Dakota and New Hampshire, report compliance rates of 90 percent or more.

Wisch said noncompliance cases are frequently investigated by the AG’s office or county prosecutors.

In May, for instance, authorities on Kauai arrested 23 sex offenders who weren’t complying with registry requirements, and asked for the public’s help to find two more.

"We want to send a very clear message that if you do not comply with laws in place, we will find you and hold you accountable," Police Chief Darryl Perry said in a statement.

Experts like Petersen, the UH professor, and Lois Perrin, legal director for the American Civil Liberties Union of Hawaii, say the state’s registry casts such a wide net that law enforcement resources are diluted and officers have a more difficult time focusing on truly dangerous offenders.

They also question the state’s approach of using what the offender is convicted of to direct registrations, rather than an assessment of the person’s threat or risk of re-offending. At least half the states use the latter approach to categorize offenders, according to a 2010 study by the Council of State Governments.

In the absence of risk assessments, Hawaii relies on a broad-brush approach, initially requiring all offenders to register for life.

Someone convicted of a first-time misdemeanor of exposing one’s private parts, for instance, basically must comply with the same registration mandates as a serial rapist, though the former can petition the court to lift the registration requirements sooner than the rapist.

"The danger of putting this all on the nature of the offense is you can have very different people caught up in the system," Petersen said. "I don’t think it makes sense, and it’s not a good use of our resources."

Perrin also said people convicted of sex crimes decades ago or of relatively insignificant offenses can have a difficult time re-integrating into society because of how they’re treated for being on the registry.

She recalled the case of an Oahu man being threatened with eviction from his apartment complex after a neighbor alerted others in the building that the man was on the registry. His conviction for sexually assaulting a minor was from the 1960s — more than 30 years before Hawaii even established a registry.

"The stories you hear about ostracization are very real," Perrin said.

Because the vast majority of sex offenders have no prior arrests and are known to their victims, a registry tends to be ineffective, given that it is compiled around the notion of a stranger with a criminal record committing offenses again, according to Kenneth Lanning, a retired FBI agent and author of the book "Child Molesters: A Behaviorial Analysis."

Yet registries often are perceived as making communities safer, Lanning and others said.

"It helps people to believe that what they are doing is providing some kind of benefit," Lanning said in a phone interview from his Virginia home. "Very often (a registry) gives many parents a false sense of security."

Like other experts, Lanning said registries would be more effective if they focused on the risk that the offenders represent, not the crimes they committed. He said law enforcement agencies aren’t given adequate resources to monitor offenders, further diminishing their effectiveness.

Wisch, the AG’s spokesman, said Hawaii’s approach of using convictions to determine registration requirements conforms with federal guidelines.

Kaneshiro, the prosecutor, likewise defended the approach. "I don’t believe there is a need to indicate a level of dangerousness, because all sex offenders are dangerous," he said.

Whatever questions there are about the effectiveness of Hawaii’s registry, people clearly check it.

According to the AG’s office, the registry website this year has received 100,000 to 130,000 hits a month, attracting 10,000 to 13,000 unique visitors monthly. Last year the monthly hits peaked at about 230,000.

Wisch said residents express their appreciation for being able to track sex offenders in their areas. People also email or call with tips, he said.