"Vietnam Requiem," the independently produced "ABC News Close-Up" at 10 tonight on Channel 7, subverts its own good intentions and squanders what appears to be a large amount of terribly powerful material. The editorial flaws in this program are so basic that it becomes almost a textbook case in muffing a great opportunity.

The failure is especially distressing because the documentary emanates from executive producer John Korty's illustrious doc shop in San Francisco. Those now working under Korty's banner have produced such exceptional pieces in the past as "Who Are the DeBolts? And Where Did They Get 19 Kids?" and "The Day After Trinity." Bill Couturie, the coproducer of "Requiem," produced 1980's unforgettable film on terminally ill children, "Can't It Be Anyone Else?," also shown as part of the "Close-Up" series.

In "Requiem," we are introduced to five Vietnam veterans who have all ended up in prison. It is explained that the arrest rate of Vietnam veterans is "almost twice" that of nonveterans in the same age group, that a Veterans Administration study has found that the more extensive a man's exposure to combat in Vietnam, the greater the chances of his involvement in crime. And we are told, again, that nearly half of those who served in Vietnam suffer some form of traumatic stress disorder.

But the precise link between combat duty in Vietnam and the fate of these five men is never clearly established; the program doesn't even look into it. The nature of the crimes committed isn't revealed until the last quarter of the show, and then, especially when one learns that two of the men are serving time for rape, a great deal more explanation is necessary than is given.

Instead of hard answers, the film, coproduced by Jonas McCord, who wrote and directed it with Couturie, wastes valuable time with flashbacks to newscasts (all ABC) from the war years and superfluous combat footage. Perhaps the combat footage is in there to avoid the dread Talking Head scourge, but these are talking heads, the five imprisoned veterans, with something to say, and the pain and horror of combat are so evident in their faces and words that film footage has the effect of cheapening, rather than heightening, the impact.

Since five men were chosen to represent Vietnam veterans in prison, a more logical (if less "arty") approach would have been to present each man's story as a segment of its own. Instead, there is much intercutting between men and the combat stuff. One man clearly dominates the program, however: Albert Alan Dobbs, an Army sergeant during the war, winner of the Purple Heart (all five men were decorated) and now serving 7 1/2 years without parole for attempted armed robbery.

Dobbs is eerily eloquent on the subjects of the war, its dehumanizing effects, and the way Vietnam veterans were treated when they returned home: "We did what we had to do, and people wanted us to be ashamed of what it made us."

He's so eloquent, he's almost prototypically tragic--the ultimate scarred vet. At one point he recalls how he gunned down a Vietnamese family because he thought they had known about a Viet Cong ambush and said nothing. "I shot a family of people," he says. "Human beings. Not for what they did. But because they happened to be in the area where something was done. Where 17 of my friends had been slaughtered. So I walked up to them and I shot them. All of them. Because--they were there . . .

"Now I see those people just as clearly every night as I did on that day."

There is more such harrowing recollection from others interviewed for the program. Duane Maybee, a Marine private, breaks down as he describes one encounter with the enemy: "I emptied a full magazine into him. Twenty rounds with an M-14. Then I stabbed him." He also says of his return to the States as a Vietnam veteran, "You get called every name in the book but the one that you're expecting." James McAllister, who served as an Army medic, recalls his anger as a black man when he returned from Vietnam and witnessed racial violence here: "I was beginning to hate. And I hated and hated." And Raymond Baker, a Marine sergeant, says in a voice quivering with resentment, "If they were going to send us into a war like that, then they should have been willing to back us all the way."

Some of what is said is redundant now--the producers seem unaware of other post-Vietnam documentaries of the past few years--but much of it is still riveting and troubling. Why should Vietnam veterans be thought of differently than veterans of other wars? It is pointed out that the average age of the combat soldier in World War II was 26, and Vietnam, 19; that those serving in Vietnam saw an average of 12 months of "hostile fire" vs. six weeks in World War II; and that, perhaps most significantly, the country was hardly divided over World War II.

And yet crucial personal and sociological data is fatally absent from "Requiem," information so crucial that its absence tends to negate the film. The veterans have been so beautifully lit and photographed that they almost lose their credibility; they seem like actors in a painstakingly sensitive play. You want to be moved by them and their stories more than you are. Ironically, the filmmakers who saw something important in these men and their plight have managed to let much of it evaporate on the way to the screen.