Colorado theater shooter James Holmes had a clean-cut appearance when he walked inside of a Centennial courthouse on Monday for the start of his death penalty trial.

Holmes, 27, is accused of killing 12 movie goers and wounding 70 others at an Aurora theater showing the "Dark Knight" movie on July 20, 2012. He has been charged with 166 counts, including first-degree murder, attempted murder and an explosives offense.

The jurors in the case will determine whether or not he was sane or insane during the shooting, and if he should be sentenced to death or life in prison, if found guilty.

According to The Associated Press, the accused mass murderer cut his signature, clown-like red hair before the trial. He also shaved off his bushy beard.

Twelve jurors and 12 alternates, which include two survivors of the 1999 Columbine shooting, were selected from an unprecedented 9,000-member jury pool, the largest in U.S. history. The nearly all-white panel consists of five men and 19 women. One of the women is Hispanic.

Among the jury are a dental assistant instructor, young mother of three, physicist and competitive shooter, and store manager at Bed Bath and Beyond, NBC News reports. In addition, a union plumber, schoolteacher, Denver Public Schools employees, a business woman and a person suffering from depression will also serve on the jury panel, reports MSNBC.

In Colorado the burden of prove falls on prosecutors to convince jurors beyond a reasonable doubt that Holmes was sane.

However, some of the survivors of the brutal attack say that Holmes deserves to be executed.

"It still doesn't bring him back, but we want justice," said W. David Hoover, who lost his 18-year-old nephew, A.J. Boik, during the shooting. "Real justice is going to happen when this animal leaves this Earth."