Six years later the door swings open. Now what?

When Robert Garza walked out of the Walls Unit of the Texas Department of Corrections after six years' incarceration, he carried one thing with him: an application to college. Mr. Garza was sentenced to 18 years in prison for the 1981 shooting death of a man with whom he had exchanged heated words outside a south Texas dance hall. During his time inside - serving at least one-third of a sentence for an aggravated offense is mandatory in Texas - the 36-year-old resident of a small town north of Corpus Christi completed a two-year college program.

His goal now, he says, the high brick walls of the prison fading behind him, is to earn a four-year business degree. But Garza feels certain he carries something else with him as he rejoins his family to begin his life anew: more maturity, and a determination to never again spend time behind bars.

``During my six years here, I've done a lot of thinking,'' Garza said during an interview a week before his release. ``This is no place for someone to be at all: It's like living hell, really. You're isolated, you lose your ability to make choices.''

Stocky, with neat, jet-black hair and pensive brown eyes, Garza says he was ``still a little wild'' when he committed his crime. His father, for whom he worked as a bookkeeper in the family trucking business, had recently died, and he and his wife had just divorced. Having served a two-year probation for possession of marijuana at 21, Garza dealt with his family problems by drinking heavily.

A recent study for the Texas Board of Pardons and Paroles shows that 80 percent of inmates entering the state system have drug- or alcohol-abuse problems. Yet Garza, like most just-released inmates, says he has learned to resist the temptations that might land him back in prison.

He says his work shining shoes in a trustee camp for the last two years was a preparation for what the inmates call the ``free world.'' Other workers in the low-security setting succumbed to a temptation to find ways to obtain drugs, or to receive sexual favors, he says. ``I lived through a very tempting employment situation,'' he says, ``so I think I'll be OK.''

The Texas Department of Corrections figures that better than 45 percent of inmates leaving Texas prisons will return to them. But Garza may be among those who make it. Unlike the typical inmate, who is a high school dropout with few skills, Garza has proved his academic abilities, having achieved a 3.46 grade point average in his college courses.

On a mid-April morning, Garza is one of 120 inmates released, each with a check for $200, from the Walls Unit. The envelope he carries as he steps into the Huntsville sunshine is an application to the University of Hawaii. Garza says he befriended another inmate whose father owns an office-cleaning business in Hawaii. His plan is to get a job with the company and complete a degree in accounting.

Going to Hawaii is attractive to Garza for another reason: He wants to start life over in a place where the baggage of the past won't be so heavy. ``I've thought about what would happen if I run into the family of the victim,'' he says, referring to his own crime. ``I intend to stay low, and I'm already making plans to leave the community. I think that will help avoid any conflict.''

The state figures Garza's incarceration cost about $12,000 a year. Garza says that in his case, the money was not well spent after three or four years. ``After that I think it risked defeating the purpose of rehabilitation,'' he says. ``If the inmate isn't rehabilitated by then, he probably never will be. He should know by then that crime doesn't pay.''

Asked, however, if the ``real world,'' including the victim's family, is likely to accept three years as a sufficient sentence, he says, ``They probably don't think six years is long enough. To me personally six years has been very long - those were supposed to be some of the most productive years of my life.'' But considering his crime, he says, ``six years doesn't seem long. I guess I don't think any one person can say what length of time is appropriate. It depends on the individual. For some, 20 years wouldn't be enough.''

Standing a few feet from the red bricks that moments before held him inside, Garza says his ``mind is in a whirl.'' His family have not arrived to pick him up. A phone call is suggested; Garza stares back dumbfounded. ``That's right, I can make a phone call,'' he says. ``It's strange not having someone looking over my shoulder, telling me what to do.''