Boston — Richard Cepulonis of Worcester and Kevin M. Murphy of Boston wanted to vote in last year's state election, but couldn't because they weren't registered. They couldn't register because they were in prison.
These inmates, and hundreds of others in correctional institutions throughout the Commonwealth, may have involuntarily sat out the last election.
The Massachusetts Supreme Judicial Court nine years ago ruled that under the state constitution, prisoners have the right to vote by absentee ballot. Now it has decreed that prisoners who weren't registered prior to their incarceration must be allowed to enroll.
Just how this is to be achieved was left to state lawmakers, among whom there appears to be little enthusiasm for adding perhaps a considerable number of convicted felons to voter ranks.
In their unanimous decision last week, the seven justices set no deadline for the legislative action, but they said it must come about ''in a timely fashion.''
A proposal for compliance with the court's decision is being readied by Massachusetts Secretary of State Michael Joseph Connolly, for submission to lawmakers by mid-September.
The two prisoners in whose behalf the registration rights suit was brought hope they will be able to vote in this fall's municipal elections in their cities. But the prospects are slim.
A measure carrying out the spirit of the court decision could be in place before the March 13 presidential preference primary. But some observers say it may not be ready even in time for the 1984 election.
Regardless of how prisoners become qualified voters - whether through mailed in applications, visits from voter registrars, or some other arrangement - they will, for such purposes, be considered residents of the city or town where they lived at the time of jailing, rather than where they are serving time. The state Supreme Court made that clear in a 1978 decision.
The possibility of convicts becoming a major political force in the community where they are incarcerated, therefore, is unlikely.
Such concerns have thwarted efforts toward voting rights for prison inmates in other states, notes Daniel E. Manville, coordinator of the American Civil Liberties Union's national prison project.
''Most states disenfranchise felons upon their conviction,'' he explains in hailing the Massachusetts ruling.
Under the United States Constitution, criteria for voter qualification are left to individual states. Less than a handful of states allow convicted felons to vote.
Nowhere, however, can voting rights be denied to those being held awaiting trial, the US Supreme Court ruled in 1975. This is in line with the US Constitution's provision that the accused are innocent until proven guilty.
Critics of allowing prisoners to enroll during their incarceration contend that if inmates were really interested in voting, they would have registered before being jailed.
But the justices ruled that ''the fact that for some inmates there once was an opportunity to register and they failed to do so, does not in our view support an absentee ballot system that has the effect of disenfranchising a group of prospective voters for a long period of time.''
Last year's Massachusetts election, in which Mr. Cepulonis and Mr. Murphy unsuccessfully sought the right to vote, was of particular interest to the state's prison population, since the ballot included the question of bringing back capital punishment. That controversial constitutional change won voter approval by a substantial margin.
It is uncertain how many of the nearly 4,600 prisoners in Massachusetts correctional institutions also were barred from voting because they were not registered and thus eligible for absentee ballots.
Cepulonis plans to organize a ''League of Prison Voters'' among his fellow inmates at state prisons, which he suggests now comprise a voting bloc that will command lawmaker attention. He hopes this group will force a harder look at prison conditions.