Defense lawyer Michael Arif said Malvo, desperate for a father figure, found the wrong man to emulate in Muhammad and eventually became "a cult of one" with Muhammad as his leader.
"Lee could no more separate himself from John Muhammad than you could separate from your shadow on a sunny day," Arif told the jury.
But prosecutor Robert F. Horan Jr. said Malvo was as responsible as Muhammad, calling the pair "peas in a pod."
"Their belief, as wild and vicious as it was, was that if they killed enough people, the government would come around" and meet their demand for $10 million, Horan said.
Malvo, 18, and Muhammad, 42, are accused of carrying out a three-week sniper spree which left 10 people dead in the Washington D.C. area last year.
Malvo is on trial for one of the killings — that of FBI analyst Linda Franklin — and faces the death penalty if convicted. In a separate trial last month, Muhammad was convicted of another of the killings and a jury recommended a death sentence.
Circuit Judge Jane Marum Roush sent the case to the jury Tuesday afternoon to begin deliberations.
CBS News reports the jury will choose a foreman today and resume deliberations tomorrow.
Malvo's attorneys have argued the teenager was temporarily insane because of Muhammad's brainwashing, causing him to blur the distinction between right and wrong.
In closing arguments, Arif told the jury that Malvo was "the last victim of John Muhammad."
But Horan said Malvo and Muhammad both share the blame.
"Their willingness to kill, and do it for money, is common to both of them," he said.
Horan urged the jury to accept Malvo's confession to police last year. Malvo subsequently recanted, telling defense psychiatrists he confessed to being the triggerman to protect Muhammad, whom he saw as a father figure.
But Horan scoffed at Malvo's backtracking, saying it came only after months of prodding from "the mental health crowd."
The jury must decide Malvo was the triggerman in Franklin's death for him to be eligible for the death penalty on one of two capital murder counts. The second capital murder count, which alleges Franklin's death was an act of terrorism, does not require that Malvo be the triggerman.
Roush ruled Tuesday that the jury will not be permitted to consider whether Malvo was acting under an "irresistible impulse."
Roush said Malvo could still go forward with his insanity defense, but denied his lawyers' request to give the jury instructions on how an irresistible impulse relates to insanity.
The law states that if a criminal cannot control an irresistible impulse, he could be considered legally insane.