A Montgomery County District Court judge postponed the trial yesterday of an elderly Bethesda couple charged with conspiracy and harboring their fugitive son after the father suffered chest pains in the courthouse.

Moments before closing arguments were to begin in the nonjury trial, David H. Christensen, 78, of 4301 East West Hwy., Bethesda, slumped in a chair in the Gaithersburg building's lobby. His 77-year-old wife, Genevieve, held his hand and gave him four pills.

"He's not doing so good," Genevieve Christensen said as he clung to her hand, breathing heavily. Minutes later, a county ambulance rushed the couple to Shady Grove Adventist Hospital, where Christensen was reported in stable condition in the intensive care unit last night.

Yesterday's incident was the latest in a series of troubles experienced by the Christensens, who prosecutors allege were trying to protect their son, William Dean Christensen, 40, from police.

The younger man has been convicted of one murder in Pennsylvania and is in prison awaiting trial on another murder charge. He also has been charged with the mutilation slayings of two women in Canada and is being investigated in connection with at least 12 murders of young women along the East Coast and in Canada from 1980 to 1983.

In August, his parents were each charged with conspiracy and harboring a fugitive after they allegedly helped their son -- mistakenly released on parole after a rape conviction in Canada -- avoid Montgomery authorities, who had a warrant for him on another rape charge.

According to the prosecution, the parents bought their son a run-down house in Philadelphia in September 1983 and paid tax, phone and utility bills for him.