Persons convicted of violating District of Columbia laws may serve substantially longer terms if they are assigned to federal rather than D.C. prisons because of different parole standards, legal defense groups told a House subcommittee yesterday.

Under the District's unique court system, federal prosecutors handle D.C. criminal cases, but those convicted may be assigned by the attorney general's office to either local or federal prisons. About 27 percent of the District's sentenced felons--about 1,200 offenders--are in federal prisons, according to city officials.

Those in federal prisons are subject to U.S. parole standards, while those in D.C. prisons are under the jurisdiction of the D.C. parole board.

The House District of Columbia subcommittee on the judiciary and education held a hearing yesterday on a bill that would transfer all parole authority over D.C. offenders to the District government. The measure was introduced by Rep. Mervyn M. Dymally (D-Calif.), the subcommittee chairman; D.C. Del. Walter E. Fauntroy and Rep. George W. Crockett Jr. (D-Mich.).

At the hearing, several defense lawyers argued that the current situation is "unfair and unconstitutional" because it subjects some prisoners to harsher parole standards not because of the type of crime they committed but simply because of where they are randomly housed.

A majority of prisoners under D.C. parole board jurisdiction are released after their minimum terms, said Joan Hartman of the Jerome N. Frank Legal Services Organization, but this is not the case in the federal system.

Mary Abigail McCarthy, supervising attorney at Yale Law School and a former staff attorney with the D.C. public defender's office, said the system discouraged prisoners at Lorton from reporting abuses they have suffered there because they are afraid they will be transferred to a federal prison for their own protection.

"A frightened inmate may be forced to remain in the general population at Lorton under unsafe conditions, and the prison administrators may be deprived of information that might assist them in identifying dangerous and violent inmates who are victimizing others," McCarthy said.

The parole transfer bill is part of the city's broader goal of getting control of all local prosecutorial and judicial functions. Yesterday, however, some city officials expressed concern that if just one part of the legal process is turned over to them, it might undermine the larger effort.

"This legislation is . . . consistent with our overall goal," said Bernice Just, D.C. parole board chairman. "However, we strongly feel that planning for a transfer of authority be undertaken as a whole rather than in incremental stages." She said this was Mayor Marion Barry's position.

One alternative to the present system would be to send D.C. parole officers to federal facilities to conduct parole hearings. That option would cost about $300,000 a year, or about $1,000 per parole candidate, Just estimated.

Other options are using U.S. parole officers to conduct the hearings under D.C. guidelines or using audio-visual technology for interviews between the D.C. parole board and federal prisoners