William Moulton Inglis was once a computer expert with the Defense Department, possessing such sensitive knowledged that the categories of his security clearances were classified.

But now the thin, pale 35-year-old Chantilly man has resigned his government job, and, after spending four months in jail because he could not post a $150,000 bond, is standing trial here on charges that he produced and distributed obscene materials for an international child pornography network.

Inglis, while still working for the Defense Communications Agency, was secretly a "lieutenant" in the pornography network, producing young boys - ages 8 to 18 - in Baltimore between 1975 and 1977 for a confederate who would photograph them in various nude and explicit sexual poses, a federal prosecutor said last week.

Inglis leaned back quietly in his chair while his defense attorney, Parker Smith, told the jury that "not much of the evidence in the trial is under dispute" and some of it is "trash."

The films and slides - some of which were shots in Inglis' Virginia apartment, according to court testimony - are not erotic enough to convict Inglis of conspiring to produce obscene material, Smith said.

"These films are boring," Smith said. "They will bore you to death. One or two are mildly erotic . . . They're disgusting. You wouldn't want to watch them.

The District Court jury of seven women and five men will have their own chance to decide whether the materials are obscene or not. About half of the 23 films in the prosecutors possession will be shown when the trial resumes this week.

The prosecution charges that Inglis helped the pornography business parly by maintaining an Arlington post office box under an assumed name. Mail orders for the movies and slides were funneled through two men in Sitzerland who relayed them to the post office box, according to the charges.

Smith said Inglis had the box long before his friends involved him in the pornography business.

"He was a member of a cult that received pictures of boys engaged in all kinds of wild activities," Smith said. "He had the box under a different name so he could enjoy them in the privacy of his own home without anyone knowing."

Two of Inglis' former pornography business associates have pladed guilty and will testify against Inglis prosecutors said.

Two have avoided arrest because they are in Switzerland. And one - the alleged masterming of the operation - David E. Houstle, 38, once Inglis' good friend, fled the country, a prosecutor said. Housle is belived to be a Gatemala, the lawyer said.