A simple eloquence rang throughout the airy lobby of the Martin Luther King Jr. Library yesterday, as more than 70 people--most of them ex-offenders--gathered for a memorial service for D. C. corrections director Delbert C. Jackson Jr.

The funeral for Jackson, attended by a host of local officials, was held Monday. But some of those who had passed through this community's prison system, along with others who have worked with offenders, wanted to say goodbye in their own words--some as crude as prison life.

The Rev. Imagene Stewart, a community organizer who runs an ex-offender shelter house in the Shaw area, called Jackson a "vanishing breed" in the face of a "lock-em-up-throw-away-the-key" approach to corrections that she said seems to be coming into vogue.

"This room should be filled with ex-offenders. This room should be running over," shouted Petey Greene, a local radio and television personality who spent 21 of his 54 years behind bars. "Delbert Jackson was one of the great ones."

Greene said that Jackson, who died at age 52 of intestinal bleeding Wednesday, was not afraid to treat inmates as human beings. Greene said he listened, always listened to what the inmates had to say.

"I'm just sorry that Delbert Jackson had to leave at such an early age," Greene said, slowly shaking his head framed with bushy sideburns. "We know wherever he's at, he's all right."

Later, after the 45-minute program, Greene said he resented Monday's "official" funeral service for Jackson, saying that it was not reflective of the man. He said the funeral, attended by Jackson's friends, family and a host of elected officials, including Mayor Marion Barry, was "too political. They politicked him all the way to his grave."

Jackson's family was not present at yesterday's service. The Rev. Lewis Anthony, an assistant to Barry, brought a message of appreciation from the family. Speaking in hushed tones, Anthony said Jackson realized that those who were being punished for breaking man's law were created by the same God that created all the world.

Rhozier (Roach) Brown's eyes were filled with tears as he spoke of Jackson. Brown is executive director of Inner Voices Inc., a community service organization that grew from a drama group he founded while serving a life sentence for murder at Lorton Reformatory. There he met Jackson.

"If it wasn't for him, I wouldn't be here today," Brown said, adding later that he probably would be dead or a narcotics addict if Jackson had not had faith in him.

When federal officials threatened to end a furlough program that would have sent Brown back to prison, Jackson bucked the system, believing he had been rehabilitated, Brown said.

As he told his story, Brown's voice tore, his eyes grew damp and red.

"Go on, go on," a woman's voice from the audience urged, "that's all right."

Brown continued: "We're going to miss Jackson in ways we'll never know possible."