Like a latter-day Don Quixote, the D.C. prison study commission has spent most of the past two months charging in vain at a giant, immovable enemy.

And, like Cervantes' well-meaning but myopic knight, the members have raged against their bricks-and-mortar foe in apparent oblivion of the futility of their efforts.

That is to say, the prison commission has voted not once but twice against building a new prison in the District, favoring instead sentencing options that would provide alternatives to incarceration.

In doing so, commission members are answering a question nobody is really asking them -- and ducking the hard choices that someone has to make.

Mayor Marion Barry says another prison has to be built and is going to be built. Barry did not come to this position enthusiastically, he points out, but he finds he has no choice.

The District's Lorton Reformatory and the D.C. Jail are overcrowded, and the city is under court order to relieve the situation. Judges are continuing to sentence convicted criminals to prison terms, something the city government cannot control, and the sentenced prisoners are coming in faster than they are going out, Barry says.

Something had to give, and what gave was Barry's long-held view that building new facilities would not help.

Sen. Arlen Specter (R-Pa.), chairman of the District appropriations subcommittee with jurisdiction over the city's annual budget, had been pushing for the prison for some time and already has added $30 million to this year's budget bill to start construction.

Enter the D.C. prison commission, with no binding authority on the issue but appointed by Barry and the City Council to help with the decisions on how big the facility should be, what security level it should have and -- clearly the most controversial issue -- where it should go.

Prisons, even with good fences, do not make popular neighbors, and residents of Ward 8 east of the Anacostia River are particularly concerned that yet another institution will be foisted on them.

City Council member Wilhelmina J. Rolark, who heads the council's Judiciary Committee and is the representative from Ward 8, is opposed to building a new prison. In creating a prison commission, Barry and Rolark reached a compromise. Whether to build a prison was included on the list of things it was to look at; the mayor appointed seven members and the council eight.

So the commission met and heard expert witnesses, and in August it took a position -- not on where or how big, but against any new prison.

Of course, the mayor had not helped matters when he said at a news conference, before the commission members were selected, that the study group might well reject the idea of a new prison.

Asked why he would appoint a study commission that might not go along with a policy decision that already had been made, and which he did not intend to change, Barry just said it was because he believed in democracy.

Despite this unaccountable mixed signal, Barry did tell commission members at an early meeting that the prison would be built. On Monday night, he again politely reminded them of that reality, telling them that the city could either make the site choices itself or have Congress impose the specifics.

"When it's all said and done, we are going to have to have more jail space," Barry told them. He asked the commission to reconsider its position, but the commission defeated a motion to reconsider by a 9-to-6 vote.

"We are making a long-range statement about what we need to do in this community," said the Rev. Eugene A. Marino, regional bishop for the Catholic Archdiocese of Washington and an opponent of a new prison. The commission is not trying to make the mayor's life more difficult, said Marino, who reminded Barry that he is not obligated to take any of the commission's advice. "If we put our heads in the sand, that prison is still going to be built." -- Joslyn Williams, AFL-CIO

"All we are doing is spinning our wheels," objected member Frank Bolden, president of the Federation of Civic Associations, who opposed the position taken by the commission. "It will be largely a waste of time."

The members did take one practical step on Monday. While voting to hold three hearings on alternative sentencing options, they agreed to one hearing on potential prison sites. This way they will at least get a look at all those sites everybody else will be considering when a real decision is to be made.

The Rev. Edward A. Hailes Sr., commission chairman, said after the Monday meeting that the group's position, in which he did not concur, did not make the commission's work moot. Members still have to consider public views and could change their minds, he said.

And Joslyn Williams, president of the AFL-CIO's Metropolitan Washington Council, said he thought that other members probably would come around eventually.

"If we put our heads in the sand, that prison is still going to be built," Williams said, but without members having any control over the location.

In the meantime, the commission must decide whether its mission is to tilt at windmills or to make a serious impact on the prison debate.