US prosecutors have begun to push for the death penalty in the case of convicted sniper John Allen Muhammad.
Muhammad has shown little emotion during the three-week trial
Prosecutor Richard Conway said the sniper lacked "a shred of remorse" after Muhammad was convicted of murder, terrorism, conspiracy and a firearms charge on Monday.
But defence lawyer Jonathan Shapiro told jurors Muhammad still had worth.
The jury is expected to hear several days of evidence before recommending a sentence to Judge LeRoy Millette.
Muhammad was convicted of shooting dead Dean Meyers at a petrol station in Manassas, Virginia, on 9 October 2002, and murdering "at least one other person".
He may also face other charges relating to the killings, which left 10 dead and three wounded in and around Washington DC.
Along with his alleged accomplice, 18-year-old Lee Boyd Malvo, Muhammad is also accused of three murders and three counts of wounding across the United States.
Mr Malvo is on trial separately.
Muhammad's ex-wife Mildred - who won custody of their three children in 2001 - is among the first set to testify in this phase of the trial in the suburbs of Washington DC.
She is likely to take the stand on Tuesday.
The defence is set to argue that Muhammad took the loss of custody of his children "extremely hard".
"You will put him in a box of one sort or another. One is made of concrete, and one is made of pine," Mr Shapiro told the jury on Monday.
Relatives of the victims welcomed the guilty verdict, and some have urged the imposition of the death penalty.
One said the case should serve to highlight the level of gun violence in the United States.
Bob Meyers, the brother of the victim at the heart of the trial, said: "I believe that capital punishment is an appropriate response in certain crimes and I must say that I can't think of too many more heinous crimes than this one."
During the trial, prosecutors portrayed Muhammad as a cold-blooded killer who trained Mr Malvo as an expert sniper before using a specially modified car to engage in a murder spree that terrorised the Washington area.
Another jury in nearby Chesapeake, Virginia, has begun hearing testimony in the trial of Mr Malvo.
He is accused of murdering FBI analyst Linda Franklin, who was shot dead on 14 October 2002 in Falls Church, Virginia.
Mr Malvo's lawyers have told jurors they will not suggest that the authorities have the wrong man, but they contend that their client is innocent by reason of insanity.
They say he was brainwashed by Muhammad, whom he
looked up to as a father figure.
Mr Malvo could also face the death penalty if convicted, despite being aged 17 at the time of his alleged crimes.