Robert Latta, the Denver water meter reader who strolled into the White House last week to get a closer look at President Reagan's swearing-in ceremonies, "hears voices" and committed himself to a mental hospital last June, according to documents filed in D.C. Superior Court.

Court records also show that a hearing commissioner's order on Jan. 21 that Latta, 45, undergo a mental evaluation was not received by city psychiatrists until three days later -- hours after he had posted bond for his release.

Latta, who was in New York yesterday taping a TV interview, expressed surprise last night on his return to Denver about the information contained in court documents and declined to discuss them.

"I'd better not," he said.

And although his attorney had said earlier that his client will return to Washington in a few weeks for a complete psychiatric exam to determine whether he is competent to stand trial, Latta wasn't so sure. "Well, I don't know," he said. "I don't have anything written."

But he said he was sure he'd go through his White House "adventure" all over again, and he was disappointed he never got to see the president.

"I just went in to attend the ceremony," said Latta, who admitted to being "surprised" when he got through the gate. "I was getting a little nervous and excited, but I thought I'd see how far I could go."

Latta, who was arrested one floor below the president's living quarters, was charged with unlawful entry of the White House, a misdemeanor, and faces a possible penalty of six months in jail and a $100 fine if convicted.

Latta carried no weapon and never actually misrepresented himself as a member of the U.S. Marine Orchestra during his White House excursion, officials said.

But his unauthorized White House visit on Jan. 20 -- he walked in with the musicians, who had come to perform for Reagan's second-term swearing-in at noon that Sunday -- embarrassed Secret Service officials and left White House aides struggling to explain the most serious intrusion into the Executive Mansion in years.

It also raised questions about how the incident went unnoticed by the media for more than a week, despite the army of reporters being marshaled that weekend to cover every aspect of the inauguration, including security arrangements. The White House confirmed details of the intrusion only after an account of it was published by Denver newspapers.

Latta was arrested shortly before 10:30 a.m., held for nearly three hours by the Secret Service in a guard station on the White House grounds and then taken to the 2nd District police station, where he was booked at 3 p.m. for "unlawful entry" at "1600 Pa. Ave. NW," the White House address.

"There was never a decision to keep it quiet," Robert Snow, a Secret Service spokesman, said yesterday. "It surprised me when it didn't come out, especially the next day on Monday when the whole thing was laid out in court."

Actually, Latta's arraignment and much of the conversation about the case in court took place at the judge's bench, according to Latta's court-appointed attorney, Peter Krauthamer.

One official in the U.S. attorney's office said yesterday he and others knew about the case but didn't realize the significance of it.

Latta was released from the D.C. Jail late Friday after he posted $1,000 bond and returned to Denver on Monday. He stayed in town through the weekend waiting to claim his wallet and other personal belongings from police.

U.S. Attorney Joseph E. diGenova criticized Latta's release, saying he should have been held for mental examination.

But Judge Fred B. Ugast, chief of the court's criminal division, said nothing was amiss in the handling of the case.

"The procedure followed was the procedure normally followed," Ugast said. "It might have taken 24 hours longer than it normally does."

Latta first appeared in court Jan. 21, the day after his arrest. Judge Robert M. Scott, handling arraignments on what was a holiday for the rest of the court, ordered Latta held in lieu of $1,000 bond and ordered him to undergo psychiatric screening the following day.

Psychiatrist Norman L. Wilson interviewed Latta in the court cell block and reported that he had told him "he wanted to enter the White House to see the president." Latta had been in a mental hospital in June, Wilson said in his report, and "he hears voices saying, 'You blew it.' "

Wilson recommended further psychiatric study of Latta's mental competence and the city's forensic psychiatrists were ordered to conduct the study within 45 days on an inpatient basis as bed space became available. A court hearing was set for March 5.

Defendants who are suicidal or who pose a danger can be committed to a mental hospital immediately, but no evidence of such urgency in Latta's case was presented.

While court clerks were processing the paper work, however, Krauthamer said he found a bondsman willing to post Latta's security bond. Several had refused, but bondsman Joe Light agreed after Latta's 79-year-old mother, who lives next door to him, wired $500 from Denver, of which Light would keep $100 as a fee.

The order for the psychiatric evaluation wasn't written until Thursday, according to court records, and psychiatrists didn't receive the order until 11:30 a.m. Friday, three hours after Light had posted Latta's bond.

Court officials said they were unable to explain the delay, but added there was nothing wrong in Latta's being released on bond.

Krauthamer refused to disclose the nature of Latta's earlier mental commitment. But in a motion filed Jan. 24, asking for a reduction in bond, he said "these actions were apparently a response to a number of problems in Mr. Latta's life."