Rada Varnovatyy took the witness stand in a Montgomery County courtroom yesterday to confront the teenager whom she said she had always considered a friend of her 15-year-old son, Kirill.

Zachary Marshall, 17, gazed blankly as Varnovatyy sobbed over the fate of her only child, the one she and her husband had brought to Gaithersburg from Ukraine in 1992 in search of a safer, better life.

Instead of befriending her son, she sobbed, Marshall "left for me the partially decomposed body of my child."

Kirill Varnovatyy, a Northwest High School sophomore, was stabbed and beaten on Labor Day 1998 in a crime that Montgomery County Circuit Court Judge Nelson W. Rupp Jr. called the most brutal slaying he could imagine. For his participation in his friend's murder, Rupp ordered Marshall to serve 30 years in prison.

While Marshall did not actually stab Kirill, the judge said, Marshall knew that another teenager planned to kill him and did nothing to stop it. The judge also noted that Marshall handed Aaron Goldfarb, 16, the knife he used to stab Kirill.

Prosecutors said Kirill had brought the switchblade to the remote Gaithersburg park and passed it around to his friends on an afternoon when he thought he was going to drink beer.

"You murdered Mr. Varnovatyy," the judge told Marshall, a former Quince Orchard High School student.

Kirill's body was discovered two weeks after he disappeared when it emerged from a storm drain in Quince Orchard Valley Park badly decomposed and wrapped in a bed sheet.

He had been beaten in the head, stabbed 28 times and almost decapitated with a slice to his throat.

Goldfarb was sentenced in September to life in prison after he pleaded guilty to first-degree murder, admitting that he was the one who stabbed Kirill. Joseph Morrongiello, 20, who, like Marshall, pleaded guilty to second-degree murder, is scheduled to be sentenced Dec. 7.

Marshall, who was 15 at the time of the slaying, apologized to Kirill's parents yesterday and told the judge that he never intended for him to die. He said he was afraid that Goldfarb would come after him, too, and that he initially believed his role in Kirill's death was "significantly limited" because he had stood by while Goldfarb did the stabbing.

"I was afraid for my life that day and, because I was afraid, another life had to be taken," Marshall said.

But the judge apparently put more weight in prosecutors' version of the events on that hot, muggy September afternoon. Deputy State's Attorney Katherine Winfree called Marshall an "active, willing participant," noting that he didn't take an opportunity to run for help after Goldfarb declared that he wanted to kill Kirill.

Winfree also noted that Marshall had struck Kirill over the head with a piece of wood before he was stabbed.

Kirill's mother broke into sobs in the front row as Winfree described how Kirill had pleaded for his life, saying, "Please don't kill me," as he was led at knifepoint for more than 45 minutes into a small clearing where no one could hear his screams.

"You killed that boy as surely as if you wielded the knife yourself, and that's what you must deal with," Winfree told Marshall.