Prosecutors believe Phillips was at the drug house, either outside or inside, at the time of the attack.
Mease, a native of Iowa, is serving federal time for possessing a firearm.
He testified that Phillips told him he wasn't at the murder scene but “was there watching.”
also testify Friday
Another witness, the defendant's former girlfriend, told a judge Phillips described the killings in such detail it gave her the impression he witnessed them.
“He liked to brag,” Kelsey Day testified.
Day said Phillips told her Brooke Phillips didn't die easily, that “she was still screaming” after being shot, stabbed and burned.
Barrientos, a drug dealer with ties to the Mexican cartel, was the intended target of the attack, prosecutors allege.
Police identified Denny Phillips as a distributor who made frequent trips to Oklahoma City to pick up drugs and take them back to the Tulsa area.
Phillips and Barrientos had a falling out in the days leading up to the slayings because Phillips owed him $30,000 and had not made payments on a car he bought from Barrientos, a third witness testified Friday.
Michael Lujan, a convicted drug dealer serving time, said Tyner did whatever Phillips told him.
Lujan testified that Tyner was looking to gain membership in the Indian Brotherhood and wouldn't have killed Barrientos unless Phillips directed him to do so.
“I figure, he needs to get what he deserves,” Lujan said as he looked in the direction of the heavily tattooed Phillips.
Prosecutors allege Phillips acted with Tyner, 30, who already has been convicted in the case.
Tyner, of Locust Grove, is serving six consecutive life terms without the possibility of parole for the murders.
Tyner was charged in 2009 and pleaded guilty in May to the murders.