After admitting he stabbed his sister to death and then set his family's Fairfax County home on fire, 22-year-old Matthew Harper was sentenced yesterday to spend the next 35 years in prison without parole for second-degree murder and arson, the maximum term allowed under a plea agreement with county prosecutors.

Speaking publicly for the first time about the Thanksgiving 1995 death of his sister, Anne E. Harper, 20, Matthew Harper told a hushed courtroom of family, friends and detectives: "When I think about my sister, I think of a beautiful young woman. I miss her every day. I can't believe I took her life, but I know that I did."

For more than three years, investigators focused on Harper as the prime suspect in the Nov. 23, 1995, blaze in the 10000 block of Ryers Place, in the Middleridge neighborhood south of Fairfax City. Harper's mother, Elizabeth Harper, fell from a second-story window and broke her back trying to escape the flames. His grandmother, Delphine Parsons, was rescued from the house by a neighbor. Matthew Harper was at his girlfriend's house, uninjured.

Firefighters found the body of Anne Harper, a junior at Rollins College, in the living room. An autopsy showed she had suffered a blow to the head and a six-inch stab wound in the back that penetrated her heart.

Harper's family refused to believe their son could have killed his sister. As detectives built a case on circumstantial evidence, Harper enrolled at James Madison University and majored in psychology. Even after he was indicted on a first-degree murder charge last fall, his family posted bond and Harper returned to Harrisonburg, where he carried a full course load and participated in campus ministry events.

But in a "version of the offense" that Harper wrote last month, he said that a January court hearing in which prosecutors laid out the details of the crime broke down his walls of denial. As he listened to witnesses, Harper wrote, "three years of convincing myself and others that I had not done this was shaken, and I asked my attorneys to begin negotiating a plea because the memories of what I did that night were awakened."

Harper wrote: "I remembered in horror that I stabbed my sister. I remembered going upstairs to tell my mother what had happened and that I could not find her. I remembered spreading gasoline. I remembered fleeing the house and the house being on fire when I fled."

In February, Harper's attorneys negotiated a plea deal, reducing the murder charge to second-degree and limiting the possible sentence to 35 years rather than the maximum 40.

In his written version and courtroom statement, Harper did not say why he killed his sister, and Deputy Commonwealth's Attorney Raymond F. Morrogh was skeptical of nearly everything Harper said. Morrogh called the crime "a brutal, savage and rather methodical killing" and noted that Harper's denial was unshaken by an earlier hearing in which photos of his sister's body were introduced as evidence.

Morrogh theorized that Harper set the fire in an attempt to collect insurance money, since he had filed several fraudulent insurance claims both before and after the fire. Morrogh said Anne Harper may have confronted her brother as he prepared to set the fire.

No one testified in Matthew Harper's behalf yesterday, though Circuit Court Judge Michael P. McWeeny received numerous letters calling for a light sentence, including two from Harper's mother. "The only possibility of redemption for me is the possibility of some kind of new life with my son," Elizabeth Harper wrote.

McWeeny spoke only briefly, calling the crime "a vicious and unexplained murder of someone you really loved."