VIRGINIA BEACH, Va. - Declaring their love for him "no matter what," John Allen Muhammad's three young children became part of the grim testimony yesterday on whether he should be sentenced to death for killings that still have no clear explanation.

"Why did you do all those shooting?" Muhammad's youngest daughter, 10-year-old Taalibah, wrote in a letter read aloud in court yesterday by her mother, Mildred Muhammad.

It was a bitter child-custody battle with Mildred Muhammad that prosecutors say sent the former soldier into a rage and possibly sparked last year's sniper rampage that spread terror in the Washington region.

Mildred Muhammad also told the jury yesterday that Taalibah recently told her, "Mommy, if Daddy gets out [of prison], then that means that he will kill you, and I don't want to live the rest of my life without my mommy."

The fear is not without foundation, Taalibah's mother said. One day in early 2000 when their marriage was falling apart, she said, John Muhammad took her into the garage of her Tacoma, Wash., home and told her, "Just know this: You have become my enemy and as my enemy, I will kill you."

Mildred Muhammad testified against her ex-husband yesterday as one of the state's final witnesses in its case for the death penalty. Jurors, who convicted the Persian Gulf war veteran of two counts of capital murder Monday, must choose a sentence of life in prison without parole or execution.

They are expected to begin deliberations late today or tomorrow.

The courtroom meeting between Mildred and John Muhammad was the first time they had seen each other since a Sept. 4, 2001, court hearing, when Mildred Muhammad won custody of the children. Prosecutors say that date marked the beginning of the convicted sniper's slow descent into violence.

Mildred Muhammad said the children's letters - delivered in envelopes bearing hand-drawn hearts - were the children's idea, and she did not tell them what to write.

Even witnesses for the defense, which began its case yesterday afternoon, said they noticed a change in Muhammad at that time. Mary Marez, a Tacoma nurse who became friends with Muhammad in 1995 and later had an intimate relationship with him, said he was desperate to find them and make sure they were all right.

"John became withdrawn, and he would sit and just stare out the window," Marez said. "He just wasn't himself. He missed them terribly."

The children have not seen their father since the 2001 court date, and their letters to him were both updates on their lives and assurances of their love. The children live with their mother in Clinton, Md., where they have followed the news of their father's trial. Mildred said she told them not to judge their father until the jury reached a verdict.

In the letter from the eldest of the three, 13-year-old John Jr. writes that he is playing full-contact football and is in a school play. He says he has more female friends than male friends, as his father had predicted. John Jr. closes his letter: "Dad, I love you so much and nothing will ever change that ever."

In her letter, 11-year-old Salena says she plays the violin, makes good grades and is in the school chorus and patrol. She writes, "I pray that I can write you a letter again. I love you very much and I always will."

Taalibah, who is 10, asks her father four questions in her letter. Besides asking why he did the shootings, she asks whether he did most of them. She asks about Muhammad's alleged accomplice, Lee Boyd Malvo, and a phrase written on a tarot card left outside the Bowie middle school where a boy was shot.

"And did you till [sic] Lee to say 'Call me God'?" she writes. Taalibah also appears to have made a heartbreaking calculation - the years until she turns 16 and would be able to visit her father in prison:

"It will be a long time until I visit you. And I love you Daddy and I always will. NO MATTER WHAT!!!!!"

Mildred Muhammad said that John Jr. told her, "Mom, if Dad takes you out, then I'm going to have to take him out." That comment was made outside the jury's presence, and the judge ruled that jurors would not be allowed to hear it.

Through much of the three hours his former wife spent on the stand, John Allen Muhammad sat with a blank stare, his right elbow resting on the defense table and his right hand supporting his chin. At one point, he flipped through family photos of him with his children - photos his lawyers later showed the jury.