Jury selection for the trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev is moving more slowly than expected as a judge probes prospective jurors on their feelings about the death penalty.

Jurors in capital cases must be willing to consider both death and life in prison. If they say they are unable to impose the death penalty or unable to consider life, they are excused from serving.

Death penalty opponents see the process as unfair. They say so-called "death-qualified" juries do not represent a true cross-section of the community.

Death penalty opponents also tend to be more willing to consider an insanity defense. That will come in to play in the trial of James Holmes, who is charged in the deadly 2012 shooting at a Colorado movie theater.