What's the Point of Calling Mattis to the Stand?

Custodia witness made a spread sheet containing all communications that he was able to pull from the devices between sunny and elizabeth. He did read some of these texts, and prosecutors read some of them too, but it doesn't sound like the prosecutors gave of context for them. And so that what that suggests to me is that prosecutors are just introducing the texts into the evidence,. They're going to come back to them later when other trial witnesses are called to the stand, and place them in context precisely m its.