More than 500 sex offenders have failed to comply with a deadline for registering with the state and now face criminal prosecution, according to the state attorney general's office.

In December, state prosecutors announced a drive to go after convicted sex offenders who do not follow the sex offender registration requirements.

Nine were indicted by an O'ahu grand jury on felony charges that could bring up to five years in prison. Since the indictments, eight of the nine have been arrested. On Jan. 22, David Baldaino, believed to be the first to plead guilty to a felony for not complying with the sex offender registry requirements, was sentenced to 30 years in prison after raping an 85-year-old woman.

In December, the attorney general's office mailed letters to 267 sex offenders — or about 13 percent of the state's 2,100 sex offenders — who had never registered. They had until Jan. 13 to sign up or face prosecution.

Of those 267, 18 registered, eight died, eight were deported to their countries of origin, 81 failed to respond and 152 of the letters were returned as unable to be forwarded. With the 294 offenders who had no verifiable address as of yesterday, that brings the total number of noncompliant sex offenders in the state to at least 527.

"We are disappointed with the response and have formed a task force composed of the Department of the Attorney General, the prosecutor's office and the police department to address the matter," said Dana Viola, special assistant to Attorney General Mark Bennett. "We had our first meeting (in January) and we are going to systematically and aggressively prosecute sex offenders who have failed to register."

The state had intended to mail out 274 letters in December, but soon learned that seven of the unregistered offenders were out of state.

The sex offender registry is maintained by the state Criminal Justice Data Center. Home addresses, work streets and ZIP codes for each offender all are available for view on the registry's Web site. The state's registered sex offenders must keep authorities updated on where they live and work.

Proponents of the attorney general's drive to register all convicted sex offenders say the database is key to keeping the community safe and informing residents of possible "risks."

Adriana Ramelli, director of the Sex Abuse Treatment Center of Hawai'i, said the database is useful for parents who fear that their child could fall prey to a pedophile or other sexual predator.

"There seems to be a concern about protecting the identity of sex offenders, but I think we need to protect our children in the community," she said. "(The registry) is one of those tools that people can use if they have any suspicion about anyone — they can just check. They may identify someone in their neighborhood or at their school, or someone who may be coaching their child. Pedophiles don't stand out in your community, so they are not easily identifiable."

The comprehensive, online registry was authorized in May 2005 after Gov. Linda Lingle signed a bill removing a requirement that sex offenders are entitled to a court hearing before their information is posted on the Internet.

A previous state Web site was shut down after the state Supreme Court ruled in 2001 that it violated due-process rights.

Voters approved a constitutional amendment in November 2004 that gave the Legislature authority to set conditions for the broader public release of the information.

Reach Peter Boylan at pboylan@honoluluadvertiser.com.