Mississippi Department of Corrections data shows Jones was moved into the 20-acre private prison for adults July 18, one day after his 22nd birthday.
Jones became an MDOC inmate May 23, 2005, after a Lee County jury convicted him in the stabbing death of his grandfather, Bertis Jones.
Sentenced to life, he spent the next six years in Walnut Grove Youth Correctional Facility in Leake County.
Family spokesman Pam Kulig of Chicago recently noted that because inmates are moved from Walnut Grove at age 22, Jones spent a couple of weeks in a Rankin County facility awaiting re-assignment.
"He says leaving Walnut Grove is like coming back from Iraq and going into a church," Kulig wrote on Facebook two days after Jones' arrival at DCF.
"He said he slept nine hours for the first time in seven years, in a deep sleep. He doesn't have to sleep with one eye open anymore. Isn't it amazing, a 15-year-old does the hardest time in this country?"
Kulig is an advocate for changing laws that allow children, like Jones was, to be charged as adults and subject to mandatory minimum sentences like life without possibility of parole.
Jones continues to wait on his petition to the Mississippi Court of Appeals for a new trial.
Last March, Jones' attorney Sylvia Owen of Tupelo pressed his case before its judges, saying his trial attorneys should have presented more evidence that the killing was self-defense.
Jones' court documents insist his original attorneys failed to show the jury an accurate layout of the kitchen, where the fight began. That could have persuaded a jury that he was trapped by the older man, with no way to escape, he claims.
Earlier appeals were turned down by the Circuit Court of Lee County and the Court of Appeals.
Born in Tupelo, Jones was 15 and living with his grandparents near Shannon in August 2004, when the altercation with his 67-year-old grandfather ended in the man's death.
Brett Jones testified he was making a sandwich when he and his grandfather got into a fight and Bertis Jones wound up stabbed eight times.
Police found his body in a utility room in the rear of the carport.