The armed robbery trial of the Rev. Bernard T. Pagano, the suspected "Gentleman Bandit," was halted unexpectedly today when a man from Pennsylvania walked into the courtroom to claim that he, not the Catholic priest, was the bendit who held up six stores last winter.

Ronald W. Clouser, a 39-year-old U.S. Postal Service employe who, a source said, has pleaded guilty to three robberies in Pennsylvania and has been treated in a mental hospital, appeared in the trial courtroom here this afternoon with his attorney, Saul H. Segan. Clouser's profile and stature are similar to Pagano's.

In a statement that stunned the courtroom audience, Segan said: "I have the authority to indicate Clouser has involvement in these acts that gave rise to the charges against Father Pagano . . . Our intention is to be as helpful as possible to exonerate Father Pagano for acts in which he was wrongly charged."

Segan noted that Clouser's statement did not amount to a confession. As of last night, Clouser had not been arrested or arraigned on the armed robbery charges, nor had Pagano's charges been dropped. The priest's fate will be uncertain until Tuesday afternoon, when defense and prosecution attorneys meet with the trial judge to decide whether the case should be dropped.

Clouser, an industrial engineering coordinator for the Postal Service, is free on bond pending sentencing for three armed robberies in Pennsylvania to which he pleaded guilty in May, according to a source close in the Pagano trial. Those robberies were similar in execution to the five holdups and one attempt that Pagano is accused of committing, the source said, and Pennsylvania police are believed to have a small, chromeplated pistol from those holdups that matches the description of the weapon used in the Delaware robberies.

Clouser has spent "some time" in a state mental hospital, according to the source, and is still under a doctor's care.

The Delaware State Police investigators who prepared the case against Pagano said they were shocked by the day's turn of events and the prosecutors had no forewarning of what was about to happen. It was clear, however, that the announcement buoyed the hopes of acquittal for Pagano.

The latest twist in this unusual trial began this afternoon just as the defense was about to begin its case. After returning from a luncheon recess, Superior Court Judge Andrew Christie strode to his bench and said: "There's been an unexpected development. An individual from Pennsylvania has confessed to committing all six of the offenses."

Many of Pagano's friends and former parishioners who had been attending his trial over the past three weeks cried when the judge made that announcement. Pagano himself nodded his head and wiped his eyes. One of his defense attorneys, Dennis Spivack, put his arm around the priest. And then Pagano shook the hands of the men and hugged and kissed the women.

Judge Christie sent the jury home and told them to come back Wednesday morning -- after his meeting with the attorneys in the case.

Several questions about Clouser remained unanswered today, such as why he decided to assert his involvement in the crimes for which Pagano is being tried. Judge Christie ordered the attorneys for both sides, and the police, to make no public comments about Clouser.

Police had said that defense attorney Carl Schnee had recently told them about a man in a Pennsylvania mental institution as a possible suspect in the "Gentleman Bandit" case. It was unclear whether Clouser is that man.

Pagano has maintained since his arrest in February that he is an innocent victim of mistaken identity. Since the trial began Aug. 7, seven witnesses to the robberies identified the tall, gaunt, bald priest as the man who calmly strolled into their stores, bought an item or two, then approached the counter, pulled out a tiny revolver and said: "Give me your money."

However, in cross-examination, defense attorney Schnee often emphasized that all but two of the witnesses were able to identify Pagano only after he was arrested and his picture appeared in the local newspapers.

Pagano, who was assistant pastor of St. Mary's Refuge of Sinners church in Cambridge, Md., at the time of his arrest, said he was "confused" by today's startling events. Although he appeared jovial tonight, in a moment of caution he said, "this is not over yet."

Earlier in the day, prosecutor Timothy Barron introduced into evidence, a men's dress hat, which was seized from Pagano's car the night he was arrested and which the prosecution maintains matched the hat the gentleman bandit frequently wore. Pagano is accused of stealing over$700 from stores in the greater Wilmington area.

In testimony last week, Det. Warren Schueler Jr., testified that Pagano, whom he has known for about a year, had approached him the day before the arrest and began asking him questions about how police investigate robberies. The next day, however, when Schueler and another detective went to Pagano's house in St. George's outside Wilmington to question him about the robberies, Pagano shut the door in Schueler's face and said he did not know him.

Later, when confronted about his prior conversation with Schueler, Pagano told police that he sometimes suffers from blackout spells.