Daryl Wayne Morse, an Air Force staff sergeant who spent more than two months in jail charged with armed rape, flew home to Hawaii a free man last week. His trial in Upper Marlboro had ended with an assistant state's attorney admitting that the man he was prosecuting could not possibly be the rapist.

Morse, 28, was arrested in Hawaii last August and charged with raping a 52-year-old Ohio woman at knife-point a month earlier in a motel near Andrews Air Force Base. Morse, the chief mechanic on a C-135 regularly flying VIPs between Andrews and Honolulu, had been staying in the same motel as the victim in a room near hers.

But after the prosecution had rested its case, prosecutor Bond E. Rhue told jurors that the defendant was clearly innocent. Morse, he said, had had a vasectomy in 1979. Because traces of spermatozoa (male reproductive cells) were found on the victim, the bedspread and a washcloth, Rhue said, and because the only person with whom the woman had had sexual relations during this period was her husband who had had a vasectomy in 1960, "inescapably a person other than this defendant is the rapist."

Rhue abandoned his prosecution after an investigator from the county public defenders' office rushed into the courtroom with key information: An examination by a Landover urologist that morning confirmed that the victim's husband could produce no sperm at all.

Morse had been examined by urologists a week earlier and had produced no sperm. But until the husband was examined, Rhue maintained the sperm could have come from the woman's encounter with her husband prior to her trip here.

Suspended without pay after his indictment in August, the nine-year Air Force veteran spent 17 days in jail in Hawaii, was extradited to Prince George's, and spent another 54 days in the county detention center before being bailed out by a fellow Air Force sergeant. If convicted, he might have faced life in prison.

But in an interview last week, Morse said he harbored no bitterness toward the woman who identified him as the rapist from the witness stand. An auditor traveling on business at the time of the rape, she had pulled his photograph from seven shown her by county detectives who drove to Ohio to interview her one week after the rape.

The woman wrote on the back of Morse's photograph: "This individual's eyes, hair, skin color look like those of the person who assaulted me, except his hair is neater in the picture. I am convinced that this is the person who raped me."

Morse, who returns to his job with the Air Force, said he believed the woman "honestly made a mistake."

But that mistake changed Morse's world. "I thought I just went down the tubes," he said. "I thought that was the end of my career."

During his months in jail, he said, he lost touch with his family and friends in Honolulu. When he was released on bond in November, he was ordered not to travel more than 10 miles from Andrews. "I haven't really seen my friends in over four months," he said.

Morse, who is divorced, said he did not know how to explain the last six months to his three children, aged 3 to 7 years, who live in Honolulu. "I'm going to have to face that in a couple of years," he said. "I've called them a couple of times. I just told them where I was [in jail]."

When he telephoned his parents in Kansas after his arrest, "I just told them I didn't do it," Morse said. "All they said was, 'We believe you.' " His friends reacted the same way, he said: "They asked me whether or not I did it. I told them no. They took me at my word."

He had never been in jail before. He made friends with some of his cell mates in the detention center, but never asked why they were locked up, and they never asked him. "I started talking to some of the guys I was locked up with," he said. "They got me into lifting weights, playing basketball. I just knew their names."

David L. Thornton, another Air Force sergeant, heard of Morse's plight from a friend in Hawaii, and although he did not know Morse, bailed him out of jail after his bond was reduced from $25,000 to $2,000, invited him to stay at his home until his trial, and gave him free use of his car. "If he was guilty, the man would have headed down to Interstate 80 with it," said Thornton, who described Morse as "a good-hearted, quiet, Kansas-type country boy."

Thornton's son, Tom, who befriended Morse, says: "The system wasn't at fault. It was the people who were controlling the system . . . . Instead of going out and trying to get somebody for the crime, they should have checked over the evidence really thoroughly."

Defense attorney James E. Kenkel, the county's chief public defender, said his argument all along was that Morse was "misidentified and completely innocent . . . . We knew where he was, and we knew scientifically that he could not have been the rapist."

But the pieces did not fall into place until about a month before the trial, he said, when an investigator for the public defender's office, a former District police detective named Howard Campbell, discovered the victim's husband also had had a vasectomy.

Kenkel said the fact Morse was wrongly arrested, charged and imprisoned "shows the built-in problem of single eyewitness identification from a photo spread. That froze [the victim's] mind, and the police stopped their investigation.

"There was never a line-up, never further investigating of other people in the motel, never any further rundown on the sub shop where Morse said he was eating with a friend at the time the rape occurred . I think the case was closed too quickly."

Prosecutor Rhue said he has thought at length about what happened and gone over all the evidence again. "Hindsight is always 20/20," he said. Part of the problem was his own lack of understanding about the relationship between sperm and vasectomies, he said.

For instance, Rhue said, he had attributed the fragmented, low levels of sperm found on the victim to the fact that she had had sexual relations with her husband the day before the rape: Only during trial testimony did he learn the sperm could be fragmented because she cleaned herself with a washcloth after the rape.

But he added that, in addition to the photo identification, there was a great deal of circumstantial evidence that seemed to link Morse to the rape. The victim said the man threatened her with a cutting blade, and Morse had used one to cut carpet earlier the same day. She said the rapist smelled fresh and had wet hair: Morse had told a coworker shortly before the time of the rape that he was going to take a shower.

Rhue also noted that Morse was wearing blue jeans and a white T-shirt at the time, the same clothes the woman said her rapist wore. Furthermore, the rapist seemed to understand the light-timing system in her room and was familiar with the motel, as Morse would have been.

Both Rhue and Kenkel said things were made more difficult by the fact that the woman and her husband lived in Ohio. Rhue was not able to meet with her until the day before the trial began, and Kenkel said he was unable to have the husband's semenal fluid tested for sperm until the last minute, because he was so far away.

But Kenkel also said the state's attorney's policy of limiting defense attorneys' access to prosecution files meant he did not know the FBI had examined the bedspread and washcloth until one week before the trial began. When he read the reports, he said, the situation "changed dramatically," he said: The sperm on these items could not have come from the victim's husband, because he was in Ohio when the rape occurred.

The woman has now returned to Ohio, and the rape case is still unsolved. Prosecutor Rhue said the woman told him she was concerned the real rapist was still loose, but was happy Morse had been cleared. "Thank God we haven't done the double wrong of convicting the wrong person," Rhue said.

Circuit Judge Albert T. Blackwell, who stopped to congratulate Morse after the trial, told jurors they should "understand that in many phases of life, and this is one of them, all of the evidence, and all of the factors sometimes are not known until a case gets into the courtroom . . . . You have had the opportunity to see that particular event occur."

One man who received Morse's gratitude was Howard Campbell, the alert investigator for the public defender's office. After the trial ended, Campbell recalls, "He walked up to me and said, 'Don't misunderstand me, but I love you.' And he gave me a kiss on the cheek."