Tracy Province testified Monday that it took three months to plan the escape with John McCluskey, but only three minutes to accomplish it.
They sparked a nationwide manhunt when they escaped with the help of an accomplice from a medium-security prison near Kingman, Ariz. in 2010.
Prosecutors say the trio targeted Gary and Linda Haas of Tecumseh, Okla., at a rest stop near the Texas-New Mexico state line.
Province has yet to testify about the killings. He is expected to testify for as many three days.
McCluskey's defense attorneys indicated in a recent motion they intend to challenge Province's credibility.