CENTENNIAL — Jury selection in the Aurora movie theater shooting trial passed a key milestone Thursday, one day after the judge said the entire trial should be finished by the end of summer.

Judge Carlos Samour and the attorneys on both sides on Thursday qualified the 68th juror to move onto the final stage of jury selection. That number is significant because it is the minimum number of jurors needed in the final phase to seat a jury.

Samour is ultimately looking for 12 jurors and 12 alternates who can fairly listen to evidence in the case. Those 24 will be chosen after one final group questioning of potential jurors — a phase scheduled to begin on April 13. During that final stage, each side will also have 22 peremptory challenges, which they can use to strike a juror without giving a reason.

Thursday marked the halfway point for the current stage of jury selection, during which Samour and the attorneys spend up to an hour questioning individual prospective jurors.

“We are right on track,” Samour said at the end of Thursday’s session.

On Wednesday, Samour told the attorneys that he expects the trial will last around four months and will likely be concluded by Labor Day. Samour said he estimates prosecutors will take about two months presenting their case and defense attorneys will take another month for theirs. If, after that, the jury finds James Holmes guilty of murder in the July 2012 attack on the Century Aurora 16 movie theater, both sides will spend another month arguing to the jury about whether Holmes should be executed.

Because of the magnitude of the case, Samour summoned an unprecedented 9,000 potential jurors. But jury selection has gone much faster than expected, and opening statements in the trial are now expected in late April, more than a month earlier than originally planned.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold