A D.C. Superior Court judge yesterday dismissed charges against a man who spent five months in jail unable to pay his bond, after the judge discovered the U.S. attorney's office had lost the man's file and had not proceeded with the case for two months.

"That's pretty troublesome," D.C. Superior Court Judge Henry F. Greene told prosecutors after dismissing felony assault charges against Roy A. Keys. "I would think the government has some responsibility to keep track of those people who are in jail" pending grand jury action.

Keys was arrested May 22 and charged with assault on a police officer after he allegedly struck an Amtrak police officer who would not allow him to use a station bathroom. Keys was unable to pay a $1,000 bond and was sent to D.C. Jail to await grand jury action.

A deputy chief of the grand jury section conceded in court yesterday that Keys' file had been misplaced and that the last action taken in the case occurred in late July when a decision was made to reduce the charges to simple assault, a misdemeanor. At that point, Assistant U.S. Attorney Joan Barton said the prosecutor handling the case must have misplaced the file, a fact unknown to anyone in the prosecutor's office until early September when Keys' attorney made inquiries about the status of the case and the prosecutor already had resigned from office.

Judge Greene scheduled yesterday's hearing after Keys' attorney, H. Heather Shaner, asked the judge to dismiss the case because of the lost file. In her motion filed in court, Shaner also said she had asked Barton Sept. 4 about the possibility of the charge becoming a misdemeanor one.

In response to Shaner's motion, Barton told the judge yesterday that the file had been found by a secretary yesterday morning and the government would like to proceed with the misdemeanor charges. Barton said Keys was a fugitive from Ohio and as a result would be locked up last night in the District anyway.

"It would be clerically simpler to keep this case alive," Barton said.

Judge Greene denied Barton's request and dismissed the case. Keys was held on the fugitive charge.

A prosecutor in the grand jury section said later yesterday afternoon that Keys would be charged today with misdemeanor assault in connection with the Amtrak incident.

A defendant can be recharged in a case if a judge dismisses an earlier charge "without prejudice" as Judge Greene did yesterday.