The harness will be in lieu of any external restraint, and will be connected to an anchor on the floor, The Denver Post reported Thursday. The visible portion of the cable on the floor will be disguised to look like a computer cable.
Holmes must remain restrained because he has been accused of "multiple violent crimes," Judge Carlos Samour Jr. said.
Also in his ruling Thursday, the judge said he'll send out 5,000 jury summons and expects at least 3,200 people to come in for jury selection when the trial begins in early February, CNN reported Friday.
It will be the state's largest jury pool in history, CNN said.
As part of Thursday's proceedings, Samour determined the 12 men and women selected to be on the jury should not be sequestered throughout the entirety of the trial, which could take a possible four months.
He said to do so would be an "unnecessarily drastic, expensive and impractical remedy that ... will create an extreme and undue hardship for jurors."
Instead, he said, jurors will not be allowed to use cellphones, tablets or laptops while in the courtroom. He also said they would be discouraged from following the trial outside the courtroom, the Post said.
Holmes faces the death penalty if convicted of murder for the attack on the Century Aurora 16 movie theater, in which 12 people were shot and killed and 58 wounded.