Detectives found bloody clothing and shoes belonging to Keith J. Gardner inside the Lorton home where police believe his parents and grandfather were stabbed to death, according to court papers made public yesterday.

As police continued to build a murder case against him, Gardner made his first court appearance in Fairfax County yesterday, four weeks after the bodies were found buried inside an underground fallout shelter behind the home at 9209 Gilmore Dr.

Gardner, 39, had recently moved in with his parents, Jimmy and Jannis Gardner, and his grandfather, Elmer Gardner. Keith Gardner has not been charged with any crimes related to the triple homicide. But in an affidavit filed yesterday, homicide Detective Richard J. Perez wrote that he believes Keith J. Gardner "is directly involved in these murders."

Perez, who flew to Pensacola, Fla., last week after Gardner was arrested there, obtained a search warrant Saturday allowing him to take a vial of Gardner's blood to compare with the blood found in the house and on Gardner's clothes.

An earlier search warrant indicated that police seized work boots from Gardner's room, as well as four knives wrapped in towels and three latex gloves with hair strands on them. Detectives also removed samples of blood from the bedrooms of the elder Gardners.

Keith Gardner had moved back home several months before the killings and was trying to kick a drug addiction, said his brother, Kim Gardner. Neighbors said they had seen Keith Gardner in and around his parents' home until May 11, the day their bodies were found, though police suspect the victims had lain in the fallout shelter for more than a week.

Yesterday's court appearance stemmed from a 1989 conviction for possession of cocaine with intent to distribute; court records state he was arrested with more than 125 grams of cocaine. Gardner served 4 1/2 years in prison, then began a 20-year probationary period. When his probation officer could not locate him after the discovery of the bodies of his parents and grandfather, a warrant was issued for Gardner's arrest for violating terms of his probation.

Gardner wore a mustache and a scruffy beard as he stood before Circuit Court Judge David T. Stitt and said he did not have enough money to hire a lawyer. Stitt appointed the public defender and ordered Gardner held without bond.

CAPTION: Keith J. Gardner has made his first court appearance since his return to Fairfax on a charge of violating probation. A judge assigned him a public defender.