While an isolated crime – no matter how sensational – doesn’t necessarily mean laws should be rewritten or public policy revamped, lawmakers are rightly reviewing the state’s sex offender registry after two men included in the online database were killed Sunday morning.

Such reviews should focus on whether the registry is serving its purpose and if it is fair. Should, for example, addresses of all offenders, no matter the severity of their crimes and how many times they have committed them, be readily available to the public?

Such questions are being asked in the wake of the shootings of 57-year- old Joseph Gray of Milo and 24-year-old William Elliott in Corinth. The assumed shooter, 20-year-old Stephen Marshall of Nova Scotia, shot himself in the head when police boarded the bus he was riding in Boston.

Both victims were included in the states online sex offender registry. According to the Maine Department of Public Safety, Mr. Marshall accessed information on the men and 32 other offenders in the registry from his laptop computer.

Mr. Elliott was listed in the registry because of a 2002 conviction for having sex with a minor. According to his mother, his girlfriend at the time was two weeks shy of her 16th birthday – the age of consent in Maine.

In 1994, Congress required states to register sex offenders and revised the law in 1996 to make the information available to the public. Since then, all but four states have created online registries. Maine is among the 31 states that include offenders’ photographs and addresses on the Web site. Accessing a registered offender’s address in Maine requires the user to provide a name and address, although this can be made up.

Some online registries include only information about those convicted of felonies, not misdemeanors like Mr. Elliott. Concerns about lumping all sex offenders into one online pool will be among the issues considered by the Criminal Justice Committee, which is meeting Tuesday to begin its review of the registry and to be updated on the investigation of the shootings. Another concern raised by several lawmakers this week was whether people with long-ago convictions should be on the list.

Rep. Stan Gerzofsky, D-Brunswick, sponsored legislation to require registration by those convicted of sex crimes since 1982. Originally, the registry went back only to 1999. Rep. Gerzofsky now says going so far back in time may have been a mistake because people who have not re-offended are suddenly being penalized and sometimes become the target of harassment after living quietly in their communities for decades.

Having a two-tiered system or an appeal process would ease this problem.

Another question should be whether the registries work. A U.S. Department of Justice review noted that while sex offender registries are popular, there has been no study of whether they make the public safer. The laws have unintended consequences ranging from making community members more anxious to harassment of sex offenders to, in last weekend’s extreme case, murder.

The Bureau of Justice Assistance Center for Program Evaluation also warned that there had not been research into whether registries cause some offenders to move to states with less restrictive registries or to areas where they are not known.

The benefits, fairness and misuse of the state’s sex offender registry are important considerations for lawmakers seeking to improve Maine’s system.