The Capital Jury Project is a big study that looks at how people are chosen to serve as jurors in really serious court cases where someone could be sentenced to death (like a murder trial). They want to learn more about the people who get picked to serve on these juries, and what they think and feel about the whole process.
When you do something wrong (like steal a cookie), you might have to go see a judge and explain what you did. But if you do something really, really bad (like hurt someone or take their life), you might have to go to court and face a big group of people called a jury. These people are chosen randomly from the community and listen to all the evidence in the case before deciding if you are guilty or not guilty.
Now, sometimes in really serious cases, the punishment could be the death penalty, which means you could be put to death as a punishment for what you did. That's what the Capital Jury Project is all about - looking at how people decided whether or not someone should get the death penalty. The project talks to these people (the jurors) and asks them what they were thinking and feeling while they were serving on the jury. This helps us understand how people make important decisions.