Colorado theater shooter James Holmes admitted he knew opening fire in a dark movie theater was "legally wrong."

Holmes, 27, is currently on trial for 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.

Holmes, who has pleaded not guilty by reason of insanity, faces the death penalty if convicted. However, in order for Holmes to receive a death sentence, prosecutors must convince the jury that the defendant knew the difference between right and wrong at the time of the alleged crime, which is called a "culpable mental state."

In a video tape that was recorded during his court-ordered sanity evaluation last year, the shooter confessed that what he did was "legally wrong."

"Was there anything about 'the mission' that said it was a wrong thing to do?" asked Dr. William Reid during the sanity examination, reports ABC Action News.

"Um, not sure," Holmes replied.

"It seems like a pretty simple question," the psychiatrist said.

"Uh, well, I knew it was legally wrong -- that you get punished for killing people," the shooter said in response.

The psychiatrist also asked the shooter what he was thinking when he was in court and found out the number of people who died and were wounded following his attack.

"Just that I was worth 12 more people than I was before," he replied.

Holmes went on to explain in a flat and emotionless voice that he gained one "value unit" for each person who died.

"I only count fatalities," Holmes said, reports The Associated Press.

Holmes went on to tell Reid that he intentionally attacked a late night PG-13 movie in order to try to limit the number of children who were killed.