An unregistered sex offender living in Haverhill, Mass., has become the first man in New Hampshire to be charged under a new federal law designed to prosecute sex offenders who cross state lines and don't tell police their new addresses.

John Collins, 38, was arraigned Tuesday in U.S. District Court on a charge he failed to register and update his registration as a sex offender.

Collins, who also had the aliases Ozzy Osbourne and John Briand, had been living in the Varnum Street area of Haverhill for approximately a month before being tracked down by the U.S. Marshals Service's New Hampshire Joint Fugitive Task Force.

"In New England, it's more of a prevalent problem," said Jeffrey White, task force coordinator. "You can have a person living in Lawrence one day and Salem another."

White said he hopes the law will help cut through some of the red tape that comes with using state laws to prosecute sex offenders who move from one state to another. He said counties are often reluctant to prosecute such cases because they have to either extradite unregistered offenders or encourage neighboring jurisdictions to prosecute sex offenders who have moved out of their area.

The new federal law has no such bounds, White said, allowing marshals to cross state lines and apprehend such offenders.

"It might even encourage some sex offenders to register," White said. "It might convince them that they don't want to get caught up with this."

Authorities were searching for Collins because he allegedly violated parole by not renewing his registration as a sex offender. He was last living in Manchester before he fell off authorities' radar.

"We weren't looking to prosecute him on this," White said. "We were looking for him on a parole violation. Our goal was to get him. He was a dangerous guy."

The Adam Walsh Act was signed into law by President Bush in July 2006.

Federal authorities used the law for the first time last fall to round up three sex offenders during a nationwide sweep that yielded 10,000 fugitives. Those three fugitives ended up not qualifying under the Walsh Act, according to White.

White said since that operation, the task force has routinely been looking for sex offenders who have stopped registering their residences.

They learned that Collins was living in Haverhill in March and arrested him at his home. White said Haverhill police had no idea Collins was living in their community. He was indicted by a federal grand jury July 11 and arraigned on the charge this week. He is scheduled to go on trial in September.

Collins pleaded guilty in September 2000 to two counts of aggravated felonious sexual assault and was sentenced to three to 10 years in state prison.

He was released on parole in May 2004, and registered with the Sex Offender Registry Board as required. In February 2006, police issued a warrant for his arrest for fleeing his last-known address in Manchester, according to U.S. marshals.