Baltimore County filed first degree murder charges yesterday against two more persons in the slayings of a witness in a federal drug case and his sister-in-law.

Charged with murder were Rodney Kelly, 18, and Janet Moore, 21, who had already been taken into custody on charges of federal civil rights violations in the case.

The move brought to four the number of people charged in the machine-gun deaths of David Scott Piechowicz and Susan Kennedy April 28 at the Pikesville hotel where they worked.

Piechowicz and his wife, Cheryl, had testified against Anthony Grandison in pretrial hearings and were scheduled to testify at his trial on heroin and cocaine distribution charges. Kennedy was filling in as a desk clerk for her sister the day of the slayings.

Grandison, who was charged with first degree murder in the case last week, was convicted of the drug charges and awaits sentencing on that conviction.

Dana Levitz, Baltimore County assistant state's attorney, said no decision had been made about seeking the death penalty against Kelly and Moore.

Baltimore County prosecutors said last week they would seek the death penalty against Vernon Evans and Grandison, both 33. Prosecutors allege Evans was paid $9,000 by Grandison to be the triggerman.