Judge D. Dortch Warriner leaned across his bench and looked down at Assistant U.S. Attorney Karen Tandy with an incredulous expression on his face.

He could not believe, he told Tandy, that a sewer trench that collapsed and took the lives of two men near Annandale two years ago, had been dug 17 feet deep, but only 13 feet wide.

"I refuse to believe that," Warriner told Tandy. "I refuse to believe that [the foreman] or anyone else would have gone down into that chasm. I know I wouldn't." What Warriner could not accept were the measurements of the trench as they had been given in court testimony by federal Occupational Safety and Health Administration (OSHA) investigator Edward Allen.

Because he found Allen's figures "fantastic" -- and because of other discrepancies in trial testimony -- Warriner on Thursday dismissed all criminal negligence charges against the S. O. Jennings Construction Corp. and its two top officers in connection with the trench collapse.

Throughout the area yesterday, government officials, inspectors and safety experts said the feds "blew it" and predicted hard times ahead for safety enforcement.

"I just can't believe it," said Fairfax County Supervisor Audrey Moore.

"I guess this is going to be a signal to the construction industry that anything goes."

But nowhere did the bitterness run more deeply than in the offices of Virginia's safety officials. They, too, had an interest in seeing the Jenningses convicted, but were never allowed to try their case.

"We were perfectly capable of handling this situation," said Charles G. Wicker, director of construction safety for the state. "We had it all worked out.They lost it, and it didn't surprise me one bit."

Wicker was particularly annoyed that the state had planned to bring civil charges against the Jenningses, but was forced to turn over all its files to the federal safety agency.

It was a state investigator, Eugene Ellison, who reached the scene of the cave-in 20 minutes after it occurred. By the time OSHA investigator Allen arrived several hours later, Ellison had already taken measurements of the trench, photographed the scene and interviewed witnesses.

But curiously, in a trial where the trench measurements proved to be crucial in the case, Ellison was never called to the stand, even though he had been subpoenaed as a prosecution witness.

State officials believe the reason Warriner never heard his testimony was because Ellison's measurements and Allen's measurements didn't match.

That Ellison was never called to the stand was one of many curiosities in a trial Warriner declared "the strangest criminal case I have ever observed."

Some who followed the case found the judge's decision consistent with his own brand of southside Virginia conservatism. "He probably represented the state's whole position regarding construction safety," said one Fairfax County official. Others, however, were convinced that government prosecutors hopelessly bungled the case.

The Jenningses' trial was only the fifth criminal case in the contry to be brought under OSHA's complex safety regulations. Though some had expected the trial to proceed quickly, it proved to be every bit as complex as the OSHA standards on which it was based.

Prosecutors had succeeded in bringing a three-count indictment against the Jenningses, charging them with "willfully and lawfully" disregarding federal safety regulations after the trench they built collapsed July 18, 1978, killing Robert Baker and Michael DeGroot.

They attempted to prove that the trench had been dug too steeply to be safe without shoring, that tons of excavated materials were piled too near the edge and that vibrations from nearby machinery prompted the cave-in.

In each case they failed miserably.

Prosecutor Tandy said in court she "had never anticipated" that the location of the cave-in would become an issue in the trial. Yet the spot was disputed by her own witnesses throughout the four-day rial.

Witnesses disagreed about the location of a tree line used by Warriner as a reference point in deciding the case. Yet Tandy did not subpoena the person responsible for drawing the line on the project's site plan. He left the court at lunchtime the last day of the trial without having been called to the stand.

Another witness, the company's one-time safety director, was not allowed to testify. The prosecution had failed to give the defense his grand jury testimony at least three days before the trial as required by court rules.

We didn't decide we were going to use this witness until Sunday night," Tandy's co-consel, Paula Newett, told Warriner. The witness said he had been subpoenaed three weeks before.

As the trial progressed, Warriner appeared increasingly angry.

He repeatedly took over the questioning from Tandy, who has been an assistant prosecutor for one year. That's the way you qualify a witness," he would snap. In his closing arguments, he admonished her for never asking witnesses where the tree line had located, and for "impeaching witnesses, then calling impeached witnesses to impeach the impeaching witnesses."

The argument over the accident's location began with Tandy's own witnesses -- Edward Allen and Larry Cosaro, the job foreman. The difference in their measurements was almost 100 feet. Warriner asked Tandy why she had permitted the dispute to begin.

But it was in Tandy's failure to comply with court orders that angered Warriner the most.

Tandy and defense attorney Guy O. Farley spent hours arguing a previous court ruling that the prosecution was obligated to provide the defense with any defendants' statements that Tandy intended to use in the trial.

After ruling once in Tandys' favor, Warriner ordered her to use her lunch hour to find all the Jenningses' statements she planned to use.

When the argument came up a third time, Warriner finally asked Tandy, "You mean you've had this case for a year and you still don't know which of the defendants' statements you intend to rely upon in the trial?"

The final blow fell when Tandy began her closing arguments against a defense motion to dismiss the case. She told the judge a mistake had been made on the original indictment.

She did not have to prove the Jenningses showed "total disregard" for their employes, Tandy said. She only had to show "plain indifference."

"You mean you waited all this time to bring that to the court's attention?" Warriner fumed.

In dismissing the case, Warriner recalled court testimony that the alleged unsafe conditions of the Jenningses' trench were commonplace in Fairfax county.

"If that's the customary and usual way in Virginia and in Fairfax County," he said, "then it is not unreasonable for the court to infer that this kind of trenching work is not ilegal."