After less than a day of deliberations, the jury ruled John McCluskey acted willfully and intentionally when he kidnapped and killed retirees Gary and Linda Haas of Tecumseh, Okla., as they passed through New Mexico on an annual camping trip to Colorado.
McCluskey, 48, sat staring toward the jury but showed no emotion when the judge read the decision.
The jury now returns Wednesday for what is expected to be weeks of additional testimony before deciding whether McCluskey should be executed or sentenced to life in prison without the possibility of parole.
Gary Haas' younger sister, Linda Rook, said death is the only fitting punishment in the case.
"He was already serving life terms, so how else can he be punished?" she said.
In its attempt to spare McCluskey's life, the defense called several neurological experts who said McCluskey is incapable of controlling his impulses and making reasoned decisions because of brain abnormalities, an abusive childhood and his long history of drug and alcohol abuse.
To be eligible for the death penalty under federal law, the jury had to find that McCluskey intentionally killed more than one person, was at least 18 and had previous convictions for violent crimes.
During closing arguments in the first phase of the penalty trial, defense attorney Teri Duncan said jurors should spare McCluskey the death penalty not of out of sympathy, but out of understanding of how his brain works and because of his inability to control his impulses.
Prosecutor Michael Warbel, however, argued McCluskey acted willfully.
"We are talking about what he intended when he pointed that gun at Gary Haas and shot him in the head," Warbel said. "We are talking about what he intended when he pointed that gun at Linda Haas and pulled the trigger twice."
The same jury on Oct. 7 convicted McCluskey of 20 counts of aggravated murder, carjacking and other charges.
McCluskey was serving 15 years for attempted second-degree murder, aggravated assault and discharge of a firearm when he and two other prisoners escaped from a medium-security prison near Kingman, Ariz., in July 2010 with the help of McCluskey's cousin and fiancee, Casslyn Welch.
One inmate quickly was captured after a shootout with authorities in Colorado, while McCluskey, Welch and inmate Tracy Province headed to New Mexico.
Testimony showed the trio was hot and cramped from three days in a small car without air conditioning. They targeted the Haases at a rest stop near the New Mexico-Texas state line for their truck and travel trailer.
Province and Welch pleaded guilty last year to carjacking resulting in death, conspiracy, the use of a firearm during a violent crime, and other charges. They both said McCluskey was the triggerman.