Colorado theater shooter James Holmes' sentencing begins Wednesday after jurors quickly convicted him of 165 counts of murder, attempted murder and other crimes stemming from his July 20, 2012, attack on a midnight movie premiere. Holmes, 27, killed 12 people and injured 70 when he opened fire, and jurors rejected his insanity defense after an 11-week trial full of heart-wrenching and gruesome testimony. Prosecutors are seeking the death penalty. Jurors' only other option is life without parole.

The penalty phase could last another month as survivors testify not just about their injuries but about the impact of the mass shooting on their lives. Here's a question-and-answer look at what happens next:

WHY WILL IT TAKE SO LONG?

There are three phases to sentencing in a Colorado death penalty case. Prosecutors begin by arguing that the circumstances of a shooting involve so-called aggravating factors that made it especially heinous. They include the killing of a child, in this case a 6-year-old girl; that Holmes was lying in wait before he opened fire; and the number of victims involved. Prosecutors expect to complete this phase on Wednesday.

THEN WHAT?

Holmes' attorneys will offer evidence of so-called mitigating factors that would warrant a life sentence over execution. They will call witnesses who can offer sympathetic testimony about Holmes' character and his life, such as his parents, former classmates and neighbors. They will also show evidence of Holmes' mental illness in an effort to show he is too sick to be executed. If jurors find beyond a reasonable doubt that the defense's mitigating factors outweigh prosecutors' aggravating factors, Holmes will be sentenced to life in prison. If not, the sentencing moves into a third phase in which victims and their relatives will describe the impacts of Holmes' crimes.

WILL HOLMES TESTIFY?

Holmes has the opportunity to testify during each of the three phases. He also has the chance to give an allocution statement, which would not be subject to cross-examination, at each of the three phases. On Tuesday, he told the judge he did not want to testify or give a statement during the first phase.

WHAT WILL IT TAKE FOR A DEATH SENTENCE?

The 12 jurors will have fewer instructions to rely on and will instead use their own personal and moral values to guide them in sentencing. If they can't unanimously agree on punishment, Holmes will automatically be sentenced to life in prison.

WILL LIFE IN PRISON BE DIFFERENT THAN DEATH ROW?

Not significantly. In Colorado, death row inmates are generally assigned to a "management control unit" where they are able to mingle with prisoners serving other sentences, including those serving life without parole.