The seven women and five men took less than six and a half hours to decide a verdict which was returned on Monday at the end of the first trial of the two men accused of the 10 killings and three woundings that terrified the Washington region in October last year.
Muhammad stood silently as the successive "guilty" answers were read out to the charges of murder, terrorism, conspiracy and illegal use of firearms. The murder and terrorism charges carry the death penalty.
The Virginia Beach trial was into the murder of Dean Meyers, who was killed by a single rifle shot as he fuelled his car in a Manassas, Virginia, self-service station on 9 October last year.
Jurors started considering a verdict on Friday and the speed of the verdict surprised some experts after the mass of evidence that was presented during the five week trial.
The defence insisted there was no clear proof Muhammad - a 42-year-old Gulf War veteran - had fired the rifle in any of the killings.
Defence insisted there was no proof Muhammad pulled trigger
But prosecutors concentrated on presenting circumstantial evidence putting Muhammad at the scene of each of the random killings.
They presented 154 witness accounts and more than 400 other pieces of evidence to back their case that Muhammad and his accused accomplice Lee Boyd Malvo toured the suburbs in a battered old car that was specially fitted out to pick off victims without being seen.
They said Muhammad and Malvo, who is being tried separately, were facing terrorism charges because they had demanded $10 million to stop the killings of housewives, bus drivers and other members of the public.
He is the first person convicted under Virginia's terrorism law, passed in the wake of the 11 September, 2001 attacks.
Judge Leroy Millette has already rejected defence claims that Muhammad should not face a possible death sentence because there was no proof that he was the "triggerman".
Hearings on the penalty to be applied started almost straight away. The process is expected to take several more days after the prosecution and defence have put their cases.
The prosecution is seeking death for both men even though Malvo was a minor when the killings were carried out between 2 and 22 October last year.
The trials of Muhammad and Malvo were moved away from Washington because it was felt an unbiased jury could not be found in the Washington area.